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初学T-SQL笔记之 ON [PRIMARY]

初学T-SQL之ON [PRIMARY]这些天什么都没做。

年前似乎有忙不完的事，年后了却又有了好逸的毛病。

今天才开始看学校实验指导的数据库开发实例。

以前一直没有时间来看。

创建表的语句中，最后总来一句on[primary]，这是什么意思？翻翻联机丛书。

在CREATE TABLE的语法下似乎没有找到。

硬着头皮看下去，终于明白了一些。

写出来吧。

侯捷老师说，发表是最好的记忆。

：）在CREATE TABLE的语法中有这样一句可选语法项目：[ ON { filegroup | DEFAULT } ]用来指定存储表的文件组。

如果指定filegroup，则表将存储在指定的文件组中。

数据库中必须存在该文件组。

如果指定DEFAULT，或者根本未指定ON 参数，则表存储在默认文件组中。

（DEFAULT 并不是关键字。

DEFAULT 是默认文件组的标识符并需对其进行定界，如ON "DEFAULT"、ON [DEFAULT]。

）ON [PRIMARY]是表示表是建立在主文件组上。

PRIMARY表示主文件组。

如果没有指定默认文件组，则主文件组是默认文件组，ON [PRIMARY]也可以省略掉了。

由数据库说开来。

Microsoft® SQL Server™ 2000 使用一组操作系统文件映射数据库，也可以说将数据库映射到一组操作系统文件上（看你怎么理解了）。

数据库中的所有数据和对象（如表、存储过程、触发器和视图）都存储在操作系统文件（数据库文件）：主要数据文件、次要数据文件和事务日志文件中。

1.主要数据文件（.MDF）该文件包含数据库的启动信息，并用于存储数据。

是数据库的起点，指向数据库中文件的其它部分。

每个数据库都有一个主要数据文件。

主要数据文件的推荐文件扩展名是 .mdf。

2.次要数据文件 (.ndf)这些文件含有不能置于主要数据文件中的所有数据即包含除主要数据文件外的所有数据文件。

有些数据库可能没有次要数据文件，而有些数据库则有多个次要数据文件。

0nv-ljyv

、.~①我们‖打〈败〉了敌人。

②我们‖〔把敌人〕打〈败〉了。

announce / E5nauns / vt.1.宣布，宣告2.声称，叙说3.预告，预示4.作播音员nounce,nunci来自拉丁文nuntiare=to declare。

announcement / E5naunsmEnt / n. 1.宣告，宣布2.（一项）公告，（一项私人）告示announcer / E5naunsE / n.广播员, 告知者, 报幕员annunciate / E5nQnFieit / vt.公布，宣布，通告denounce / di5nauns / vt.1.公开谴责，指责2.控告，告发denunciation / dInQnsI5eIF(E)n / n.1.公开谴责，指责2.控告，告发enunciate / i5nQnsieit / vi./vt.1.清晰地念，清晰地发音2.清晰发言，阐明pronounce / prE5nauns / vt.1.发音2.注音3.宣布,宣判4.发言，发表意见pronunciation / prE7nQnsi5eiFEn / n.1.发音2.读法,发音方法pronounced / prE5naunst / a.1.发音的,讲出来的2.显著的，清楚的，明确的renounce / ri5nauns / vt.1.声明放弃,抛弃2.宣布中止3.拒绝,否认逻辑辨证记忆提示：由nounce,nunci演化而来的英文单词围绕着“todeclare（宣布，声称）”造词。

这组词很好理解，推理也很简单，但前提是要熟练掌握前缀的用法，如pronouce的“显著的，清楚的，明确的”之意，若不知道“pro-”可指“程度上的前”。

重点词经典真题例句：We all know what an advertisement is, it's essentially a message that announces something for sale.（02.L）我们大家都知道，一个广告本质上是一条宣布某些事物被出售的信息。

sqlserver uniqueidentifier 遍历 -回复

sqlserver uniqueidentifier 遍历-回复SQL Server中的uniqueidentifier类型是用于存储全局唯一标识符（GUID）的数据类型。

GUID是一种128位长的标识符，它可以在数据库中唯一地标识一条记录。

本文将一步一步回答关于SQL Server uniqueidentifier类型的问题，并探讨它的用途、生成方式以及在数据库中的应用。

第一步：什么是uniqueidentifier类型？uniqueidentifier类型是SQL Server中的一种数据类型，用于存储GUID 值。

GUID全称是全局唯一标识符（Globally Unique Identifier），它是由一个32位的十六进制数表示，以连字符分隔成五个部分，形式如：xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx。

第二步：uniqueidentifier类型的用途是什么？uniqueidentifier类型在数据库中的主要用途是作为主键或唯一标识符。

每当插入一条新记录时，可以使用NEWID()函数生成一个唯一标识符，并将其赋给uniqueidentifier列。

这样就可以保证每个记录都有一个全局唯一的标识符，避免出现重复数据。

第三步：uniqueidentifier类型的生成方式是什么？在SQL Server中，可以使用NEWID()函数来生成一个新的唯一标识符。

该函数会返回一个新的uniqueidentifier值，它是根据计算机上的网络地址、当前时间和随机数生成的。

由于这些因素的独特性，生成的GUID几乎可以保证全局唯一。

第四步：uniqueidentifier类型在数据库中的应用是什么？在数据库中，uniqueidentifier类型可以用作主键或唯一标识符列。

与其他类型的主键相比，使用uniqueidentifier类型的主键可以更好地保证数据的唯一性。

此外，在数据库中使用uniqueidentifier类型作为主键还可以提供更好的数据分布和查询性能。

牛津词典语法表示符号

使用语法标识与缩写a.adjective 形容词adv. Adverb 副词art.Article 冠词conj. Conjunction 连词int.interjection 感叹词n.noun 名词prep. preposition 介词pron. pronoun 代词v.verb 动词vi. intranstive verb 不及物动词vt.transtive verb 及物动词C——可数名词U——不可数名词CGp——可数集合名词Gp——-集合名词sing v——复数名词与单数动词连用pl v——单数名词与复数动词连用sing or pl v-复数名词与单数或复数动词均可连用pl——复数名词与复数动词连用sing——单数名词与单数动词连用attrib——用作定语pred——用作表语La——系动词+形容词Ln——系动词+名词I——不及物动词Ipr——不及物动词+介词短语Ip——不及物动词+副词小词In/pr——不及物动词+名词/介词短语It——不及物动词+带to的不定式Tn——及物动词+名词——及物动词+名词+介词短语——及物动词+名词+副词小词Tf——及物动词+限定式that从句Tw——及物动词+从句或短语Tt——及物动词+带to的不定式Tnt——及物动词+名词+带to的不定式Tg——及物动词+动词-ing成分TSg——及物动词+名词（’s）+动词-ing成分Tng——及物动词+名词+动词-ing成分Tni——及物动词+名词+不带to的不定式——复合及物动词+名词+形容词——复合及物动词+名词+名词a——复合及物动词+名词+名词或形容词——复合及物动词+名词+带to的不定式——复合及物动词+名词+动词-ing成分——复合及物动词+名词+不带to的不定式——双及物动词++名词+介词短语——双及物动词+名词+介词短语——双及物动词+名词+限定式that从句——双及物动词+介词短语+限定式that从句——双及物动词+名词+wh-从句或短语——双及物动词+介词短语+从句或短语——双及物动词+名词+带to的不定式——双及物动词+介词短语+带to的不定式。

SPAN与RSPAN详解

SPAN与RSPAN详解SPAN RSPAN⼀、SPAN简介SPAN技术主要是⽤来监控交换机上的数据流，⼤体分为两种类型，本地SPAN和远程SPAN.----Local Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN)，实现⽅法上稍有不同。

利⽤SPAN技术我们可以把交换机上某些想要被监控端⼝（以下简称受控端⼝）的数据流COPY或MIRROR⼀份，发送给连接在监控端⼝上的流量分析仪，⽐如CISCO的IDS或是装了SNIFFER⼯具的PC. 受控端⼝和监控端⼝可以在同⼀台交换机上（本地SPAN），也可以在不同的交换机上（远程SPAN）。

⼆、名词解释SPAN Session——SPAN会话：SPAN会话是指⼀组受控端⼝与⼀个监控端⼝之间的数据流。

可以同时对多个端⼝的进⼊流量或是⼀个端⼝的外出流量进⾏监控，也可以对VLAN内所有端⼝的进⼊流量进⾏监控，但不能同时对多个端⼝的外出流量及VLAN的外出流量进⾏监控，可以对处于关闭状态的端⼝设置SPAN，但此时的SPAN会话是⾮活动，但只要相关的接⼝被打开，SPAN就会变为活动的。

监控端⼝最好是>=受控端⼝的带宽，否则可能会出现丢包的情况。

SPAN Traffic——SPAN的流量：使⽤本地SPAN可以监控所有的⽹络流量，包括multicast、bridge protocol data unit （BPDU），和CDP、VTP、DTP、STP、PagP、LACP packets. RSPAN不能监控⼆层协议。

Traffic Types——流量类型：被监控的流量类型分为三种，Receive （Rx） SPAN 受控端⼝的接收流量，Transmit （Tx）SPAN 受控端⼝的发送流量，Both ⼀个受控端⼝的接收和发送流量。

Source Port——SPAN会话的源端⼝（也就是monitored port-即受控端⼝）：受控端⼝可以是实际的物理端⼝、VLAN、以太通道端⼝组EtherChannel，物理端⼝可以在不同的VLAN中，受控端⼝如果是VLAN则包括此VLAN中的所以物理端⼝，受控端⼝如果是以太通道则包括组成此以太通道组的所有物理端⼝，如果受控端⼝是⼀个TRUNK⼲道端⼝，则此TRUNK端⼝上承载的所有VLAN流量都会受到监控，也可以使⽤filter vlan 参数进⾏调整，只对filter vlan 中指定的VLAN数据流量做监控。

MYSQL的索引类型：PRIMARY,INDEX,UNIQUE,FULLTEXT,SPAI。。。

MYSQL的索引类型：PRIMARY,INDEX,UNIQUE,FULLTEXT,SPAI。

⼀、介绍⼀下索引的类型Mysql常见索引有：主键索引、唯⼀索引、普通索引、全⽂索引、组合索引PRIMARY KEY（主键索引） ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` ) UNIQUE(唯⼀索引) ALTER TABLE`table_name` ADD UNIQUE (`column`)INDEX(普通索引) ALTER TABLE `table_name` ADD INDEX index_name ( `column` ) FULLTEXT(全⽂索引) ALTER TABLE`table_name` ADD FULLTEXT ( `column` )组合索引 ALTER TABLE `table_name` ADD INDEX index_name ( `column1`, `column2`, `column3` )Mysql各种索引区别：普通索引(INDEX)：最基本的索引，没有任何限制唯⼀索引(UNIQUE)：与"普通索引"类似，不同的就是：索引列的值必须唯⼀，但允许有空值。

主键索引(PRIMARY)：它是⼀种特殊的唯⼀索引，不允许有空值。

全⽂索引(FULLTEXT )：仅可⽤于 MyISAM 表，⽤于在⼀篇⽂章中，检索⽂本信息的, 针对较⼤的数据，⽣成全⽂索引很耗时好空间。

组合索引：为了更多的提⾼mysql效率可建⽴组合索引，遵循”最左前缀“原则。

举个例⼦来说，⽐如你在为某商场做⼀个会员卡的系统。

这个系统有⼀个会员表有下列字段：会员编号 INT会员姓名 VARCHAR(10)会员⾝份证号码 VARCHAR(18)会员电话 VARCHAR(10)会员住址 VARCHAR(50)会员备注信息 TEXT那么这个会员编号，作为主键，使⽤ PRIMARY会员姓名如果要建索引的话，那么就是普通的 INDEX会员⾝份证号码如果要建索引的话，那么可以选择 UNIQUE （唯⼀的，不允许重复）会员备注信息，如果需要建索引的话，可以选择 FULLTEXT，全⽂搜索。

venn包用户指南说明书

Package‘venn’October12,2022Version1.11Date2022-06-09Title Draw Venn DiagramsDepends R(>=3.5.0)Imports admisc(>=0.10)Suggests QCA(>=3.9),ggplot2,ggpolypathDescriptionDraws and displays Venn diagrams up to7sets,and any Boolean union of set intersections. License GPL(>=3)URL https:///dusadrian/vennBugReports https:///dusadrian/venn/issuesNeedsCompilation noAuthor Adrian Dusa[aut,cre,cph](<https:///0000-0002-3525-9253>)Maintainer Adrian Dusa<*********************>Repository CRANDate/Publication2022-06-0821:30:02UTCR topics documented:About the venn package (2)getCentroid (2)getZones (3)venn (5)Index1112getCentroidAbout the venn packageDraw Venn DiagramsDescriptionDraws and displays Venn diagrams up to7sets,and any boolean union of set intersections. DetailsPackage:vennType:PackageVersion: 1.11Date:2022-06-09License:GPL(>=2)Author(s)Authors:Adrian DusaDepartment of SociologyUniversity of Bucharest<*********************>Maintainer:Adrian DusagetCentroid Calculate the centroid of a polygon.DescriptionThis function takes a list of dataframes or a matrices containing x and y values,which deﬁne zones (polygons),and calculates their centroids.UsagegetCentroid(data)Argumentsdata A matrix or a dataframe with two columns,for x and y coordinatesDetailsMost of the coordinates for the intersection labels in this package were calculated using the formula for a centroid of a non-self-intersecting closed polygon,approximated by10vertices.ValueA list with x and y coordinates,for each zone in the input list.ReferencesCentroid.(n.d.).In Wikipedia.Retrieved January06,2016,from https:///wiki/Centroid Examplesvenn("0110")#centroid for the intersection"0110"in a4set diagramcentroid<-getCentroid(getZones("0110"))[[1]]text(centroid[1],centroid[2],labels="0110",cex=0.85)#centroids for the two zones in the"E not A"zonesvenn(5)area<-getZones("0---1")#list of length2polygon(area[[1]],col="lightblue")polygon(area[[2]],col="lightblue")text(do.call("rbind",getCentroid(area)),labels=c("zone1","zone2"),cex=0.85)getZones Calculate the union(s)of set intersections.DescriptionThis function uses a metacommand to calculate the shape of a speciﬁc zone or a list of zones.UsagegetZones(area,snames,ellipse=FALSE)Argumentsarea A chgaracter expression written in sum of products form.snames A string containing the sets’names,separated by commas.ellipse Logical,get the zones from the shape of an ellipse,where possibleDetailsA SOP("sum of products")is also known as a DNF("disjunctive normal form"),or in other wordsa"union of intersections",for example A*D+B*c.The same expression can be written in curly brackets notation:A{1}*D{1}+B{1}*C{0}.The expression B{1}*C{0}can also be written in a pseudo-language,as"-10-"(assuming there are only four sets).A"zone"is a union of set intersections.There are exactly2^k intersections in a Venn diagram, where k is the number of sets.To highlight an entire set,we need a union of all possible intersections which form that set.The argument ellipse retrieves the data from the shape of an ellipse,and it only works with4and 5sets.ValueA list of self-enclosed polygons,for each independent zone.Examplesvenn(3)area<-getZones("A",snames="A,B,C")#a list of length1polygon(area[[1]],col="lightblue")#The very same result is obtained with:zone<-getZones("1--")#for5sets,the content of the5th set but not in the first set is a#list of two zonesvenn(5)zones<-getZones("0---1")#this time a list of length2#(re)coloring the first zone(union)polygon(zones[[1]],col="lightblue")venn5 #and the second zone(union)polygon(zones[[2]],col="lightblue")venn Draw and display a Venn diagramDescriptionThis function uses a variety of input data to draw and display a Venn diagram with up to7sets.Usagevenn(x,snames="",counts,ilabels=FALSE,ellipse=FALSE,zcolor="bw",opacity=0.3,plotsize=15,ilcs=0.6,sncs=0.85,borders=TRUE,box=TRUE,par=TRUE,ggplot=FALSE,...)Argumentsx A single number(of sets),or a metacommand formula(see details),or a list containing set values,or a dataset containing boolean values.snames An optional parameter containing the names for each set.ilabels Logical:print the labels for each intersection.counts A numerical vector of counts for each set intersection.ellipse Logical,force the shape to an ellipse,where possiblezcolor A vector of colors for the custom zones,or predeﬁned colors if"style"opacity Degree of opacity for the color(s)speciﬁed with zcolor(less opacity,more transparency).plotsize Plot size,in centimeters.ilcs Character expansion(in base plots)or size(in ggplots)for the intersection labels sncs Character expansion(in base plots)or size(in ggplots)for the set namesborders Logical:draw all intersection bordersbox Logical:draw the outside squarepar Logical:use the default,custom par settingsggplot Logical:plot the Venn diagram using ggplot...Additional parameters,mainly for the outer borders of the sets6vennDetailsThe argument x can be either:-a single number(of sets),between1and7-a metacommand(character)to draw custom intersection zones-a list,containing values for the different sets:each component is a set,and only up to7compo-nents are processed.-a dataset of boolean values.A"zone"is a union of set intersections.There are exactly2^k intersections in a Venn diagram, where k is the number of sets.To highlight an entire set,we need a union of all possible intersections which form that set.For example,in a3sets diagram,the(overall)ﬁrst set is composed by four intersections:100for what is in theﬁrst set but outside sets2and outside set3101for the intersection between sets1and3,outside set2110for the intersection between sets1and2,outside set3111for the intersection between all three sets.A meta-language can be used to deﬁne these intersections,using the values of1for what is insidethe set,0for what is outside the set,and-when its either inside or outside of the set.The command"1--"is translated as"display only theﬁrst,entire set"is equivalent with the union of the four intersections"100+101+110+111".The parameter snames should have the same length as the number of sets speciﬁed by the parameter x.When the parameter x is used as a metacommand,the number of sets is calculated as the number of characters in each intersection of the metacommand.One such character command is"100+101+ 110+111"or"1--",and all intersections have exactly three characters.It is also possible to use a regular,disjunctive normal form,like"A",which is equivalent with"Abc +AbC+ABc+ABC".When x is an expression written in DNF,if a valid R statement then quoting is not even necessary.The argument snames establishes names for the different sets,or in its absence it is taken from LETTERS.When x is a list or a dataframe,snames is taken from their names.The length of the snames indicates the total number of sets.A numerical vector can be supplied with the argument counts,when the argument x is a singlenumber of sets.The counts should match the increasing order of the binary representation for the set intersections.When the argument x is a list,the counts are taken from the number of common values for each intersection,and when x is a data frame,(comprised of exclusively boolean values 0and1)the counts are taken from the number of similar rows.If a particular intersection does not have any common values(or no rows),the count"0"is left blank and not displayed in the diagram.The argument ellipse differentiates between two types of diagrams for4and5sets.The idea is to allow for as much space as possible for each intersection(also as equal as possible)and that is impossible if preserving the shape of an ellipse.The default is to create large space for the intersections,but users who prefer an ellipse might want to set this argument to TRUE.Colors toﬁll the desired zones(or entire sets)can be supplied via the argument zcolor(the default is"bw"black and white,which means no colors at all).Users can either chose the predeﬁned color style,using zcolor="style",or supply a vector of custom colors for each zone.If only one custom color is supplied,it will be recycled for all zones.venn7When using zcolor="style",any other additional arguments for the borders are ignored.A different set of predeﬁned colors is used,when argument x is a QCA type object(a truth table,either from a class tt or from a class qca).If custom colors are provided via zcolor,it should havea length of3colors:theﬁrst for the absence of the outcome(0),the second for the presence of theoutcome(1),and the third for the contradictions(C).Remainders have no color,by default.The argument ilcs works only if the intersection labels(ilabels)or intersection counts are acti-vated,and it sets the size of the labels via a cex argument.In the absence of a speciﬁc value from the user,it’s default is set to0.6for all Venn diagrams with up toﬁve sets,and it automatically decreases to0.5for six sets and0.45for seven sets.Via...,users can specify additional parameters,mainly for the outer borders of the sets,as speci-ﬁed by par(),and since version1.9it is also used to pass additional aesthetics parameters for the ggplot2graphics.All of them are feeded either to the base function lines()which is responsible with the borders,or to the function geom_path()from package ggplot2.For up to3sets,the shapes can be circular.For more than3sets,the shape cannot be circular:for 4and5sets they can be ellipses,while for more than5sets the shapes cannot be continous(they might be monotone,but not continous).The7sets diagram is called"Adelaide"(Ruskey,2005).The most challenging diagram is the one with6sets,where for many years it was thought a Venn diagram didn’t even exist.All diagrams are symetric,except for the one with6sets,where some of the sets have different shapes.The diagram in this package is an adaptation from Mamakani,K., Myrvold W.and F.Ruskey(2011).The argument border can be used only for custom intersections and/or unions,it has no effect when x is a list,or a data frame,or a truth table object.The argument par is used to deﬁne a custom set of parameters when producing the plot,to ensurea square shape of about15cm and eliminate the outer regions.If deactivated,users can deﬁne theirown size and shape of the plot using the system function par().By default,the plot is always produced using a size of1000points for both horizontal and vertical,unless the argument ggplot is activated,when the argument par will have no effect.ReferencesRuskey,F.and M.Weston.2005.Venn diagrams.Electronic Journal of Combinatorics,Dynamic Survey DS5.Mamakani,K.,Myrvold W.and F.Ruskey.2011.Generating all Simple Convexly-drawable Po-lar Symmetric6-Venn Diagrams.International Workshop on Combinatorial Algorithms,Victoria.LNCS,7056,275-286.Examples#A simple Venn diagram with3setsvenn(3)#with a vector of counts:1for"000",2for"001"etc.venn(3,counts=1:8)#display the first whole setvenn("1--")8venn #same withvenn("A",snames="A,B,C")#an equivalent command,from the union of all intersectionsvenn("100+110+101+111")#same withvenn("A~B~C+AB~C+A~BC+ABC")#adding the labels for the intersectionsvenn("1--",ilabels=TRUE)#using different parameters for the bordersvenn(4,lty=5,col="navyblue")#using ellipsesvenn(4,lty=5,col="navyblue",ellipse=TRUE)#a5sets Venn diagramvenn(5)#a5sets Venn diagram using ellipsesvenn(5,ellipse=TRUE)#a5sets Venn diagram with intersection labelsvenn(5,ilabels=TRUE)#and a predefined color stylevenn(5,ilabels=TRUE,zcolor="style")#a union of two setsvenn("1----+----1")#same withvenn("A+E",snames="A,B,C,D,E")#with different colorsvenn("1----,----1",zcolor="red,blue")#same withvenn("A,E",snames="A,B,C,D,E",zcolor="red,blue")#same colors for the bordersvenn("1----,----1",zcolor="red,blue",col="red,blue")#6sets diagramvenn(6)#7sets"Adelaide"venn(7)venn9 #artistic versionvenn(c("1000000","0100000","0010000","0001000","0000100","0000010","0000001","1111111"))#without all bordersvenn(c("1000000","0100000","0010000","0001000","0000100","0000010","0000001","1111111"),borders=FALSE)#using sum of products notationvenn("A+B~C",snames="A,B,C,D")#when x is a listset.seed(12345)x<-list(First=1:20,Second=10:30,Third=sample(25:50,15))venn(x)#when x is a dataframeset.seed(12345)x<-as.data.frame(matrix(sample(0:1,150,replace=TRUE),ncol=5))venn(x)#producing a ggplot2graphicsvenn(x,ggplot=TRUE)#increasing the border sizevenn(x,ggplot=TRUE,size=1.5)#with dashed linesvenn(x,ggplot=TRUE,linetype="dashed")##Not run:#produce Venn diagrams for QCA objectslibrary(QCA)data(CVF)obj<-truthTable(CVF,"PROTEST",incl.cut=0.85)venn(obj)#to set opacity based on inclusion scores#(less inclusion,more transparent)venn(obj,opacity=obj$tt$incl)#custom labels for intersectionspCVF<-minimize(obj,include="?")10venn venn(pCVF$solution[[1]],zcol="#ffdd77,#bb2020,#1188cc")cases<-paste(c("HungariansRom","CatholicsNIreland","AlbaniansFYROM","RussiansEstonia"),collapse="\n")coords<-unlist(getCentroid(getZones(pCVF$solution[[1]][2])))text(coords[1],coords[2],labels=cases,cex=0.85)##End(Not run)Index∗functionsgetCentroid,2getZones,3venn,5∗packageAbout the venn package,2About the venn package,2geom_path,7getCentroid,2getZones,3lines,7par,7venn,5venn_package(About the venn package),211。

ensrnop编号

ensrnop编号English Answer:ENSEMBL Transcript ID (ENST), also known as ENSEMBL Transcript Identification Number or ENSRNO, is a unique identifier assigned to each transcript model in the ENSEMBL database. It is a stable and versioned identifier that remains the same across ENSEMBL releases, allowing users to track and reference specific transcript models over time.ENSTs are composed of two parts:1. ENSEMBL Gene ID (ENSG): A stable and versioned identifier assigned to each gene model in the ENSEMBL database.2. Transcript version number: A numeric version number that indicates the specific version of the transcript model.ENSTs are typically used for the following purposes:Identifying and referencing specific transcript models in scientific publications and databases.Tracking changes and updates to transcript models over time.Performing comparative analyses of transcript models across different species or tissues.Developing and validating gene expression assays and other molecular biology techniques.中文回答：ENSEMBL 转录序列号 (ENST)，也称为 ENSEMBL 转录序列识别号或 ENSRNO，是分配给 ENSEMBL 数据库中每个转录本模型的唯一标识符。

primary造句

primary造句1、He made no mention of primary colors.他没有提到基色。

2、Science didactics in primary schools in one of these subjects.小学理科教授法系其中的一科。

3、The pool identified as the reclamation storage pool must bea primary sequential storage pool.回收存储池的池的类型必须是主顺序存储池。

4、A natural preservative CP-F was prepared by using hesperidinas primary raw material.用桔皮提取物橙皮甙为主要原料制备了天然果蔬护色保鲜剂CP - F。

5、Psyllium offers benefits in patients with irritable bowel syndromein primary care.欧车前在肠易激综合征患者的初级保健中疗效最佳。

6、Primary election has been running for months.初选已经开始了几个月。

7、It comes in bright primary colours that kids will love.它的颜色都是孩子们喜爱的亮丽原色。

8、Shorter light incubation time always causes high primary production and assimilation number.短的曝光时间往往带来高的初级生产力和同化系数。

9、Parody constructs one of the primary features of postmodernist fiction.戏仿是后现代主义小说的一个主要特征。

英语语用学名词解释

1.Pragmatics is the study of language in use.Pragmaticsis concerned with the study of meaning as communicated by a speaker (or writer) and interpreted by a listener (or reader).Pragmatics is the study of speaker meaningPragmatics is the study of contextual meaningPragmaticsis the study of the expression of relative distance.Pragmatics is the study of the relationships between linguistic forms and the users of those forms.2.Syntax is the study of the relationships between linguistic forms, how they are arranged in sequence, and whichsequences are well-formed.3.Semantics is the study of the relationships between linguistic forms and entities in the world; that is, how wordsliterally connect to things.4.Deixis指示语is a technical term (from Greek) for one of the most basic things we do with utterances. It means‘pointing’ via language.Any linguistic form used to accomplish this ‘pointing’ is called a deictic expression. Deictic expressions are also sometimes called indexicals. They are among the first forms to be spoken by very young children and can be used to indicate people via person deixis(such as, ‘me’, ‘you’), or location via spatial deixis(such as ‘here’, ‘there’), or time via temporal deixi s (such as ‘now’, ‘then’).5.Proximal terms近指are typica lly interpreted in terms of the speaker’s location, or the deictic center指示中心.‘this’,‘there’, ‘now’, ‘then’near speaker6.Distal terms远指can simply indicate ‘away’ from speaker’, but, in some languages, can be used to distinguishbetween ‘near addressee’ and ‘away from both speaker and addressee’.7.Person deixis人称指示语clearly operates on a basic three-part division, exemplified例证by the pronouns for firstperson, second person, and third person./ forms used to point to people, “me””you”8.Expressions which indicate addressee higher status are described as honorifics敬语.9.The discussion of the circumstances which lead to the choice of one of these forms rather than another is sometimesdescribed as social deixis./forms used to indicate relative social status10.A distinction between forms used for familiar versus a non-familiar addressee in some languages. This is known as theT/V distinction.用复数形态来表示单数敬语，在语言中叫T-V distinction。

SCI Bias Resistor Transistors数据手册说明书

MUN5312DW1,NSBC124EPDXV6,NSBC124EPDP6 Complementary Bias Resistor TransistorsR1 = 22 k W, R2 = 22 k WNPN and PNP Transistors with Monolithic Bias Resistor NetworkThis series of digital transistors is designed to replace a single device and its external resistor bias network. The Bias Resistor Transistor (BRT) contains a single transistor with a monolithic bias network consisting of two resistors; a series base resistor and a base-emitter resistor. The BRT eliminates these individual components by integrating them into a single device. The use of a BRT can reduce both system cost and board space.Features•Simplifies Circuit Design•Reduces Board Space•Reduces Component Count•S and NSV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements;AEC-Q101 Qualified and PPAP Capable*•These Devices are Pb-Free, Halogen Free/BFR Free and are RoHS CompliantMAXIMUM RATINGS(T A = 25°C both polarities Q1 (PNP) & Q2 (NPN), unless otherwise noted) Rating Symbol Max Unit Collector-Base Voltage V CBO50Vdc Collector-Emitter Voltage V CEO50Vdc Collector Current − Continuous I C100mAdc Input Forward Voltage V IN(fwd)40Vdc Input Reverse Voltage V IN(rev)10Vdc Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality should not be assumed, damage may occur and reliability may be affected.ORDERING INFORMATIONDevice Package Shipping†MUN5312DW1T1G,SMUN5312DW1T1G*SOT−3633,000 / Tape & Reel NSVMUN5312DW1T3G*SOT−36310,000 / Tape & ReelMUN5312DW1T2G,NSVMUN5312DW1T2G*SOT−3633,000 / Tape & ReelNSBC124EPDXV6T1G,NSVBC124EPDXV6T1G*SOT−5634,000 / Tape & Reel NSBC124EPDXV6T5G SOT−5638,000 / Tape & Reel NSBC124EPDP6T5G SOT−9638,000 / Tape & Reel†For information on tape and reel specifications, including part orientation andtape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D.MARKING DIAGRAMSPIN CONNECTIONS12/R=Specific Device CodeM=Date Code*G=Pb-Free Package (Note: Microdot may be in either location) *Date Code orientation may vary depending upon manufacturing location.SOT−363CASE 419B−02SOT−563CASE 463A(1)(2)(3)(6)(5)(4)SOT−963CASE 527ADM1R12 M GG1612 M G1THERMAL CHARACTERISTICSCharacteristic Symbol Max Unit MUN5312DW1 (SOT−363) ONE JUNCTION HEATEDTotal Device DissipationT A = 25°C(Note1)(Note2)Derate above 25°C(Note1)(Note2)P D1872561.52.0mWmW/°CThermal Resistance,(Note1) Junction to Ambient(Note2)R q JA670490°C/WMUN5312DW1 (SOT−363) BOTH JUNCTION HEATED (Note3)Total Device DissipationT A = 25°C(Note1)(Note2)Derate above 25°C(Note1)(Note2)P D2503852.03.0mWmW/°CThermal Resistance,Junction to Ambient(Note1)(Note2)R q JA493325°C/WThermal Resistance, Junction to Lead(Note1)(Note2)R q JL188208°C/WJunction and Storage Temperature Range T J, T stg−55 to +150°C NSBC124EPDXV6 (SOT−563) ONE JUNCTION HEATEDTotal Device DissipationT A = 25°C(Note1)Derate above 25°C(Note1)P D3572.9mWmW/°CThermal Resistance,Junction to Ambient(Note1)R q JA350°C/WNSBC124EPDXV6 (SOT−563) BOTH JUNCTION HEATED (Note3)Total Device DissipationT A = 25°C(Note1)Derate above 25°C(Note1)P D5004.0mWmW/°CThermal Resistance,Junction to Ambient(Note1)R q JA250°C/WJunction and Storage Temperature Range T J, T stg−55 to +150°C NSBC124EPDP6 (SOT−963) ONE JUNCTION HEATEDTotal Device DissipationT A = 25°C(Note4)(Note5)Derate above 25°C(Note4)(Note5)P D2312691.92.2MWmW/°CThermal Resistance,Junction to Ambient(Note4)(Note5)R q JA540464°C/WNSBC124EPDP6 (SOT−963) BOTH JUNCTION HEATED (Note3)Total Device DissipationT A = 25°C(Note4)(Note5)Derate above 25°C(Note4)(Note5)P D3394082.73.3MWmW/°CThermal Resistance,Junction to Ambient(Note4)(Note5)R q JA369306°C/WJunction and Storage Temperature Range T J, T stg−55 to +150°C1.FR−4 @ Minimum Pad.2.FR−*****×1.0 Inch Pad.3.Both junction heated values assume total power is sum of two equally powered channels.4.FR−4 @ 100mm2, 1 oz. copper traces, still air.5.FR−4 @ 500mm2, 1 oz. copper traces, still air.ELECTRICAL CHARACTERISTICS (T A =25°C both polarities Q 1 (PNP) & Q 2 (NPN), unless otherwise noted)CharacteristicSymbolMinTypMaxUnitOFF CHARACTERISTICS Collector-Base Cutoff Current (V CB =50V, I E =0)I CBO −−100nAdcCollector-Emitter Cutoff Current (V CE =50V, I B =0)I CEO −−500nAdcEmitter-Base Cutoff Current (V EB =6.0V, I C =0)I EBO −−0.2mAdcCollector-Base Breakdown Voltage (I C =10m A, I E =0)V (BR)CBO 50−−VdcCollector-Emitter Breakdown Voltage (Note 6)(I C =2.0mA, I B =0)V (BR)CEO50−−VdcON CHARACTERISTICS DC Current Gain (Note 6)(I C =5.0mA, V CE =10V)h FE 60100−Collector-Emitter Saturation Voltage (Note 6)(I C =10mA, I B =0.3mA)V CE(sat)−−0.25VInput Voltage (Off)(V CE =5.0V, I C =100m A) (NPN)(V CE =5.0V, I C =100m A) (PNP)V i(off)−− 1.21.2−−VdcInput Voltage (On)(V CE =0.2V, I C =5.0mA) (NPN)(V CE =0.2V, I C =5.0mA) (PNP)V i(on)−− 1.92.0−−VdcOutput Voltage (On)(V CC =5.0V, V B =2.5V, R L =1.0k W )V OL −−0.2VdcOutput Voltage (Off)(V CC =5.0V, V B =0.5V, R L =1.0k W )V OH 4.9−−VdcInput Resistor R115.42228.6k WResistor RatioR 1/R 20.81.01.2Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product performance may not be indicated by the Electrical Characteristics if operated under different conditions.6.Pulsed Condition: Pulse Width =300ms, Duty Cycle ≤2%.Figure 1. Derating CurveAMBIENT TEMPERATURE (°C)P D , P O W E R D I S S I P A T I O N (m W )(1) SOT−363; 1.0×1.0 Inch Pad (2) SOT−563; Minimum Pad(3) SOT−963; 100mm 2, 1 oz. Copper TraceFigure 2. V CE(sat) vs. I CFigure 3. DC Current GainFigure 4. Output Capacitance Figure 5. Output Current vs. Input VoltageFigure 6. Input Voltage vs. Output Current1.60.80V R , REVERSE VOLTAGE (V)0.41.22.02.42.83.2C o b , O U T P U T C A P A C I T A N C E (p F )0.010.001I C , COLLECTOR CURRENT (mA)V C E (s a t ), C O L L E C T O R -E M I T T E R V O L T A G E (V )h F E , D C C U R R E N T G A I N10001001I C , COLLECTOR CURRENT (mA)10I C , C O L L E C T O R C U R R E N T (m A )1001010.10.010.001V in , INPUT VOLTAGE (V)V i n , I N P U T V O L T A G E (V )I C , COLLECTOR CURRENT (mA)1010.1100C o b , O U T P U T C A P A C I T A N C E (p F )Figure 7. V CE(sat) vs. I CFigure 8. DC Current GainFigure 9. Output Capacitance Figure 10. Output Current vs. Input VoltageFigure 11. Input Voltage vs. Output Current10320V R , REVERSE VOLTAGE (V)456789 0.001I C , COLLECTOR CURRENT (mA) 0.11V C E (s a t ), C O L L E C T O R -E M I T T E R V O L T A G E (V ) 0.01h F E , D C C U R R E N T G A I NI C , COLLECTOR CURRENT (mA)1I C , C O L L E C T O R C U R R E N T (m A )100101 0.1 0.01 0.001V in , INPUT VOLTAGE (VOLTS)V i n , I N P U T V O L T A G E (V )I C , COLLECTOR CURRENT (mA)1Figure 12. V CE(sat) vs. I CI C , COLLECTOR CURRENT (mA)10010.1Figure 13. DC Current GainFigure 14. Output CapacitanceI C , COLLECTOR CURRENT (mA)10001001I C , COLLECTOR CURRENT (mA)Figure 15. Output Current vs. Input Voltage1001010.10.01V in , INPUT VOLTAGE (V)Figure 16. Input Voltage vs. Output Current0.41.20V R , REVERSE VOLTAGE (V)V C E (s a t ), C O L L E C T O R −E M I T T E R V O L T A G E (V )h F E , D C C U R R E N T G A I N 0.81.62.02.4C o b , O U T P U T C A P A C I T A N C E (p F )I C , C O L L E C T O R C U R R E N T (m A )V i n , I N P U T V O L T A G E (V )1010Figure 17. V CE(sat) vs. I CFigure 18. DC Current GainI C , COLLECTOR CURRENT (mA)I C , COLLECTOR CURRENT (mA)0.010.11Figure 19. Output CapacitanceFigure 20. Output Current vs. Input VoltageV R , REVERSE VOLTAGE (V)V in , INPUT VOLTAGE (V)Figure 21. Input Voltage vs. Output CurrentI C , COLLECTOR CURRENT (mA)V C E (s a t ), C O L L E C T O R −E M I T T E R V O L T A G E (V )h F E , D C C U R R E N T G A I NC o b , O U T P U T C A P A C I T A N C E (p F )I C , C O L L E C T O R C U R R E N T (m A )V i n , I N P U T V O L T A G E (V )SC−88/SC70−6/SOT−363CASE 419B−02ISSUE YNOTES:1.DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.2.CONTROLLING DIMENSION: MILLIMETERS.3.DIMENSIONS D AND E1 DO NOT INCLUDE MOLD FLASH,PROTRUSIONS, OR GATE BURRS. MOLD FLASH, PROTRU-SIONS, OR GATE BURRS SHALL NOT EXCEED 0.20 PER END.4.DIMENSIONS D AND E1 AT THE OUTERMOST EXTREMES OF THE PLASTIC BODY AND DATUM H.5.DATUMS A AND B ARE DETERMINED AT DATUM H.6.DIMENSIONS b AND c APPLY TO THE FLAT SECTION OF THE LEAD BETWEEN 0.08 AND 0.15 FROM THE TIP .7.DIMENSION b DOES NOT INCLUDE DAMBAR PROTRUSION.ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.08 TOTAL IN EXCESS OF DIMENSION b AT MAXIMUM MATERIAL CONDI-TION. THE DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OF THE FOOT.DIM MIN NOM MAX MILLIMETERS A −−−−−− 1.10A10.00−−−0.10dddb 0.150.200.25C 0.080.150.22D 1.80 2.00 2.20−−−−−−0.0430.000−−−0.0040.0060.0080.0100.0030.0060.0090.0700.0780.086MIN NOM MAX INCHES0.100.004E1 1.15 1.25 1.35e 0.65 BSC L 0.260.360.462.00 2.10 2.200.0450.0490.0530.026 BSC0.0100.0140.0180.0780.0820.086*For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D.SOLDERING FOOTPRINT*DIMENSIONS: MILLIMETERS0.306XRECOMMENDEDSIDE VIEWEND VIEWPLANEDETAIL AE A20.700.90 1.000.0270.0350.039L20.15 BSC 0.006 BSC aaa 0.150.006bbb 0.300.012ccc 0.100.0046XH EDIMMIN NOM MAX MILLIMETERS A 0.500.550.60b 0.170.220.27C D 1.50 1.60 1.70E 1.10 1.20 1.30e 0.5 BSC L 0.100.200.301.50 1.60 1.700.0200.0210.0230.0070.0090.0110.0590.0620.0660.0430.0470.0510.02 BSC0.0040.0080.0120.0590.0620.066MIN NOM MAX INCHESSOT−563, 6 LEADCASE 463A ISSUE GNOTES:1.DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982.2.CONTROLLING DIMENSION: MILLIMETERS3.MAXIMUM LEAD THICKNESS INCLUDES LEAD FINISH THICKNESS. MINIMUM LEAD THICKNESS IS THE MINIMUM THICKNESS OF BASE MATERIAL.ǒmm inchesǓSCALE 20:1*For additional information on our Pb−Free strategy and solderingdetails, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D.SOLDERING FOOTPRINT*0.080.120.180.0030.0050.007SOT−963CASE 527AD ISSUE EDIM MIN NOM MAX MILLIMETERS A 0.340.370.40b 0.100.150.20C 0.070.120.17D 0.95 1.00 1.05E 0.750.800.85e 0.35 BSC 0.95 1.00 1.05H E ANOTES:1.DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994.2.CONTROLLING DIMENSION: MILLIMETERS3.MAXIMUM LEAD THICKNESS INCLUDES LEAD FINISH THICKNESS. MINIMUM LEADTHICKNESS IS THE MINIMUM THICKNESS OF BASE MATERIAL.4.DIMENSIONS D AND E DO NOT INCLUDE MOLD FLASH, PROTRUSIONS, OR GATE BURRS.TOP VIEW SIDE VIEWDIMENSIONS: MILLIMETERSRECOMMENDEDMOUNTING FOOTPRINT*L 0.19 REF L20.050.100.156X *For additional information on our Pb-Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D.ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries.ON Semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor’s product/patent PUBLICATION ORDERING INFORMATION。

IPC-7351B & PCBL Land Pattern Naming Convention

I P C-7351B N a m i n g C o n v e n t i o n f o r S t a n d a r d S M T L a n d P a t t e r n sSurface Mount Land PatternsComponent, Category Land Pattern Name Ball Grid Array’s...............................BGA + Pin Qty + C or N + Pitch P + Ball Columns X Ball Rows _ Body Length X Body Width X Height BGA w/Dual Pitch.BGA + Pin Qty + C or N + Col Pitch X Row Pitch P + Ball Columns X Ball Rows _ Body Length X Body Width X Height BGA w/Staggered Pins..................BGAS + Pin Qty + C or N + Pitch P + Ball Columns X Ball Rows _ Body Length X Body Width X Height BGA Note: The C or N = Collapsing or Non-collapsing BallsCapacitors, Chip, Array, Concave..........................................................CAPCAV + Pitch P + Body Length X Body Width X Height - Pin Qty Capacitors, Chip, Array, Flat..................................................................CAPCAF + Pitch P + Body Length X Body Width X Height - Pin Qty Capacitors, Chip, Non-polarized.................................................................................................CAPC + Body Length + Body Width X Height Capacitors, Chip, Polarized.....................................................................................................CAPCP + Body Length + Body Width X Height Capacitors, Chip, Wire Rectangle........................................................................................CAPCWR + Body Length + Body Width X Height Capacitors, Molded, Non-polarized...........................................................................................CAPM + Body Length + Body Width X Height Capacitors, Molded, Polarized.................................................................................................CAPMP + Body Length + Body Width X Height Capacitors, Aluminum Electrolytic ............................................................................................................CAPAE + Base Body Size X Height Ceramic Flat Packages.....................................................................................................CFP127P + Lead Span Nominal X Height - Pin Qty Column Grid Array’s.....................................................CGA + Pitch P + Number of Pin Columns X Number of Pin Rows X Height - Pin Qty Crystals (2 leads)........................................................................................................................XTAL + Body Length X Body Width X Height Dual Flat No-lead..........................................................................................................DFN + Body Length X Body Width X Height – Pin Qty Diodes, Chip................................................................................................................................DIOC + Body Length + Body Width X Height Diodes, Molded...........................................................................................................................DIOM + Body Length + Body Width X Height Diodes, MELF................................................................................................................................DIOMELF + Body Length + Body Diameter Fuses, Molded............................................................................................................................FUSM + Body Length + Body Width X Height Inductors, Chip.............................................................................................................................INDC + Body Length + Body Width X Height Inductors, Molded........................................................................................................................INDM + Body Length + Body Width X Height Inductors, Precision Wire Wound................................................................................................INDP + Body Length + Body Width X Height Inductors, Chip, Array, Concave..............................................................INDCAV + Pitch P + Body Length X Body Width X Height - Pin Qty Inductors, Chip, Array, Flat......................................................................INDCAF + Pitch P + Body Length X Body Width X Height - Pin Qty Land Grid Array, Round Lead............................LGA + Pin Qty - Pitch P + Pin Columns X Pin Rows _ Body Length X Body Width X Height Land Grid Array, Square Lead........................LGAS + Pin Qty - Pitch P + Pin Columns X Pin Rows _ Body Length X Body Width X Height LED’s, Molded............................................................................................................................LEDM + Body Length + Body Width X Height Oscillators, Side Concave........................................................................OSCSC + Pitch P + Body Length X Body Width X Height - Pin Qty Oscillators, J-Lead.......................................................................................OSCJ + Pitch P + Body Length X Body Width X Height - Pin Qty Oscillators, L-Bend Lead.............................................................................OSCL + Pitch P + Body Length X Body Width X Height - Pin Qty Oscillators, Corner Concave....................................................................................................OSCCC + Body Length X Body Width X Height Plastic Leaded Chip Carriers..................................................PLCC + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height - Pin Qty Plastic Leaded Chip Carrier Sockets Square.......................PLCCS + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height - Pin Qty Quad Flat Packages..................................................................QFP + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height - Pin Qty Ceramic Quad Flat Packages.................................................CQFP + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height - Pin Qty Quad Flat No-lead................................................................QFN + Pitch P + Body Width X Body Length X Height - Pin Qty + Thermal Pad Pull-back Quad Flat No-lead..............................................PQFN + Pitch P + Body Width X Body Length X Height - Pin Qty + Thermal Pad Quad Leadless Ceramic Chip Carriers..........................................................LCC + Pitch P + Body Width X Body Length X Height - Pin Qty Quad Leadless Ceramic Chip Carriers (Pin 1 on Side)...............................LCCS + Pitch P + Body Width X Body Length X Height - Pin Qty Resistors, Chip...........................................................................................................................RESC + Body Length + Body Width X Height Resistors, Molded......................................................................................................................RESM + Body Length + Body Width X Height Resistors, MELF...........................................................................................................................RESMELF + Body Length + Body Diameter Resistors, Chip, Array, Concave............................................................RESCAV + Pitch P + Body Length X Body Width X Height - Pin Qty Resistors, Chip, Array, Convex, E-Version (Even Pin Size)...............RESCAXE + Pitch P + Body Length X Body Width X Height - Pin Qty Resistors, Chip, Array, Convex, S-Version (Side Pins Diff)................RESCAXS + Pitch P + Body Length X Body Width X Height - Pin Qty Resistors, Chip, Array, Flat.....................................................................RESCAF + Pitch P + Body Length X Body Width X Height - Pin Qty Small Outline Diodes, Flat Lead...................................................................................SODFL + Lead Span Nominal + Body Width X Height Small Outline IC, J-Leaded........................................................................................SOJ + Pitch P +Lead Span Nominal X Height - Pin Qty Small Outline Integrated Circuit, (50 mil Pitch SOIC)......................................................SOIC127P +Lead Span Nominal X Height - Pin Qty Small Outline Packages............................................................................................SOP + Pitch P +Lead Span Nominal X Height - Pin Qty Small Outline No-lead...........................................................SON + Pitch P + Body Width X Body Length X Height - Pin Qty + Thermal Pad Pull-back Small Outline No-lead.........................................PSON + Pitch P + Body Width X Body Length X Height - Pin Qty + Thermal Pad Small Outline Transistors, Flat Lead....................................................................SOTFL + Pitch P + Lead Span Nominal X Height - Pin Qty SOD (Example: SOD3717X135 = JEDEC SOD123)........................................................SOD + Lead Span Nominal + Body Width X Height SOT89 (JEDEC Standard Package).......................................................................................................................................................SOT89 SOT143 & SOT343 (JEDEC Standard Package)..............................................................................................................SOT143 & SOT343 SOT143 & SOT343 Reverse (JEDEC Standard Package)...........................................................................................SOT143R & SOT343R SOT23 & SOT223 Packages (Example: SOT230P700X180-4)...............................SOT + Pitch P + Lead Span Nominal X Height - Pin Qty TO (Generic DPAK - Example: TO228P970X238-3).................................................................TO + Pitch P + Lead Span X Height - Pin QtyI P C-7351B L a n d P a t t e r n N a m i n g C o n v e n t i o n N o t e s•All dimensions are in Metric Units•All Lead Span and Height numbers go two places past the decimal point and “include” trailing Zeros•All Lead Span and Body Sizes go two place before the decimal point and “remove” leading Zeros•All Chip Component Body Sizes are one place to each side of the decimal point•Pitch Values are two places to the right & left of decimal point with no leading Zeros but include trailing zeros N a m i n g C o n v e n t i o n S p e c i a l C h a r a c t e r U s e f o r L a n d P a t t e r n sThe _ (underscore) is the separator between pin Qty in Hidden & Deleted pin componentsThe – (dash) is used to separate the pin qty.The X (capital letter X) is used instead of the word “by” to separate two numbers such as height X width like “Quad Packages”.P C B L i b r a r i e s S u f f i x N a m i n g C o n v e n t i o n f o r L a n d P a t t e r n sCommon SMT Land Pattern to Describe Environment Use (This is the last character in every name)Note: This excludes the BGA component family as they only come in the Nominal Environment Condition •M.................Most Material Condition (Level A)•N..................Nominal Material Condition (Level B)•L.................Least Material Condition (Level C)Alternate Components that do not follow the JEDEC, EIA or IEC Standard•A..................Alternate Component (used primarily for SOP & QFP when Component Tolerance or Height is different) •B..................Second Alternate ComponentReverse Pin Order•-20RN..........20 pin part, Reverse Pin Order, Nominal EnvironmentHidden Pins•-20_24N......20 pin part in a 24 pin package. The pins are numbered 1 – 24 the hidden pins are skipped. The schematic symbol displays up to 24 pins.Deleted Pins•-24_20N......20 pin part in a 24 pin package. The pins are numbered 1 – 20. The schematic symbol displays 20 pins. JEDEC and EIA Standard parts that have several alternate packages•AA, AB, AC.JEDEC or EIA Component IdentifierGENERAL SUFFIXES_HS.........................HS = Land Pattern with Heat Sink attachment requiring additional holes or padsExample: TO254P1055X160_HS-6N_BEC......................BEC = Base, Emitter and Collector (Pin assignments used for three pin Transistors)Example: SOT95P280X160_BEC-3N_SGD......................SGD = Source, Gate and Drain (Pin assignments used for three pin Transistors)Example: SOT95P280X160_SGD-3N_213........................213 = Alternate pin assignments used for three pin TransistorsExample: SOT95P280X160_213-3NP C B L i b r a r i e s N a m i n g C o n v e n t i o n f o r N o n-S t a n d a r d S M T L a n d P a t t e r n s Surface Mount Land PatternsComponent, Category Land Pattern Name Amplifiers....................................................................................................................................................AMP_ Mfr.’s Part Number Batteries......................................................................................................................................................BAT_ Mfr.’s Part Number Capacitors, Variable..................................................................................................................................CAPV_Mfr.’s Part Number Capacitors, Chip, Array, Concave (Pins on 2 or 4 sides)..............................................................CAPCAV_Mfr Series No. - Pin Qty Capacitors, Chip, Array, Flat (Pins on 2 sides)..............................................................................CAPCAF_Mfr Series No. - Pin Qty Capacitors, Miscellaneous............................................................................................................................CAP_Mfr.’s Part Number Crystals......................................................................................................................................................XTAL_Mfr.’s Part Number Diodes, Miscellaneous...................................................................................................................................DIO_Mfr.’s Part Number Diodes, Bridge Rectifiers............................................................................................................................DIOB_Mfr.’s Part Number Ferrite Beads..................................................................................................................................................FB_Mfr.’s Part Number Fiducials......................................................................................................................................FID + Pad Size X Solder Mask Size Filters..............................................................................................................................................................FIL_Mfr.’s Part Number Fuses..........................................................................................................................................................FUSE_Mfr.’s Part Number Fuse, Resettable.....................................................................................................................................FUSER_Mfr.’s Part Number Inductors, Miscellaneous...............................................................................................................................IND_Mfr.’s Part Number Inductors, Chip, Array, Concave (Pins on 2 or 4 sides)..................................................................INDCAV_Mfr Series No. - Pin Qty Inductors, Chip, Array, Flat (Pins on 2 sides).................................................................................INDCAF_Mfr Series No. - Pin Qty Keypad.................................................................................................................................................KEYPAD_Mfr.’s Part Number LEDS............................................................................................................................................................LED_Mfr.’s Part Number LEDS, Chip...................................................................................................................................................LED_Mfr.’s Part Number Liquid Crystal Display...................................................................................................................................LCD_Mfr.’s Part Number Microphones..................................................................................................................................................MIC_Mfr.’s Part Number Opto Isolators............................................................................................................................................OPTO_Mfr.’s Part Number Oscillators......................................................................................................................................OSC_Mfr.’s Part Number - Pin Qty Quad Flat Packages w/Bumper Corners, Pin 1 Side.............BQFP + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height - Pin Qty Quad Flat Packages w/Bumper Corners, 1 Center..............BQFPC + Pitch P + Lead Span L1 X Lead Span L2 Nominal X Height - Pin Qty Resistors, Chip, Array, Concave (Pins on 2 or 4 sides).................................................................RESCAV_Mfr Series No. - Pin Qty Resistors, Chip, Array, Convex Type E (Pins on 2 sides)...........................................................RESCAXE_Mfr Series No. - Pin Qty Resistors, Chip, Array, Convex Type S (Pins on 2 sides)...........................................................RESCAXS_Mfr Series No. - Pin Qty Resistors, Chip, Array, Flat (Pins on 2 sides)................................................................................RESCAF_Mfr Series No. - Pin Qty Relays.....................................................................................................................................................RELAY_Mfr.’s Part Number Speakers....................................................................................................................................................SPKR_Mfr’s Part Number Switches........................................................................................................................................................SW_Mfr.’s Part Number Test Points, Round......................TP + Pad Size (1 place left of decimal and 2 places right of decimal, Example TP100 = 1.00mm) Test Points, Square...............................................................TPS + Pad Size (1 place left of decimal and 2 places right of decimal) Test Points, Rectangle....................................TP + Pad Length X Pad Width (1 place left of decimal and 2 places right of decimal) Thermistors.............................................................................................................................................THERM_Mfr.’s Part Number Transceivers.............................................................................................................................................XCVR_ Mfr.’s Part Number Transducers (IRDA’s)................................................................................................................................XDCR_Mfr.’s Part Number Transient Voltage S_Mfr.’s Part Number Transient Voltage Suppressors, SP_Mfr.’s Part Number Transistor Outlines, Custom....................................................................................................................TRANS_Mfr.’s Part Number Transformers.............................................................................................................................................XFMR_Mfr.’s Part Number Trimmers & Potentiometers........................................................................................................................TRIM_Mfr.’s Part Number Tuners.....................................................................................................................................................TUNER_Mfr.’s Part Number Varistors.......................................................................................................................................................VAR_Mfr.’s Part Number Voltage Controlled Oscillators.....................................................................................................................VCO_Mfr.’s Part Number Voltage Regulators, Custom......................................................................................................................VREG_Mfr.’s Part NumberI P C-7251N a m i n g C o n v e n t i o n f o r T h r o u g h-H o l e L a n d P a t t e r n sThe land pattern naming convention uses component dimensions to derive the land pattern name.The first 3 – 6 characters in the land pattern name describe the component family.The first number in the land pattern name refers to the Lead Spacing or hole to hole location to insert the component lead.All numbers that follow the Lead Spacing are component dimensions.These characters are used as component body identifiers that precede the value and this is the priority order of the component body identifiers –P = Pitch for components with more than two leadsW = Maximum Lead Width (or Component Lead Diameter)L = Body Length for horizontal mountingD = Body Diameter for round component bodyT = Body Thickness for rectangular component bodyH = Height for vertically mounted componentsQ = Pin Quantity for components with more than two leadsR = Number of Rows for connectorsA, B & C = the fabrication complexity level as defined in the IPC-2221 and IPC-2222Notes:All component body values are in millimeters and go two places to the right of the decimal point and no leading zeros.All Complexity Levels used in the examples are “B”.Component, Category Land Pattern Name Capacitors, Non Polarized Axial Diameter Horizontal Mounting.........CAPAD + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: CAPAD800W52L600D150BCapacitors, Non Polarized Axial Diameter; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Capacitors, Non Polarized Axial Rectangular.........CAPAR + Lead Spacing + W Lead Width + L Body Length + T Body thickness + H Body Height Example: CAPAR800W52L600T50H70BCapacitors, Non Polarized Axial; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Thickness 0.50; Body Height 0.70Capacitors, Non Polarized Axial Diameter Vertical Mounting .........CAPADV + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: CAPADV300W52L600D150BCapacitors, Non Polarized Axial; Lead Spacing 3.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50mmCapacitors, Non Polarized Axial Rect. Vert. Mtg.CAPARV + Lead Spacing + W Lead Width + L Body Length + T Body Thickness + H Body Height Example: CAPARV300W52L600T50H70BCapacitors, Non Polarized Axial Rect. Vertical; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Thickness 0.50; Body Height 0.70 Capacitors, Non Polarized Radial Diameter.......................................CAPRD + Lead Spacing + W Lead Width + D Body Diameter + H Body Height Example: CAPRD200W52D300H550BCapacitors, Non Polarized Radial Diameter; lead spacing 2.00; lead width 0.52; Body Diameter 3.00; Height 5.50Capacitors, Non Polarized Radial Rectangular.......CAPRR + Lead Spacing + W Lead Width + L Body Length + T Body thickness + H Body Height Example: CAPRR200W52L50T70H550BCapacitors, Non Polarized Radial Rectangular; lead spacing 2.00; lead width 0.52; Body Length 0.50; Body thickness 0.70; Height 5.50 Capacitors, Non Polarized Radial Disk Button........CAPRB + Lead Spacing + W Lead Width + L Body Length + T Body thickness + H Body Height Example: CAPRB200W52L50T70H550BCapacitors, Non Polarized Radial Rectangular; lead spacing 2.00; lead width 0.52; Body Length 0.50; Body thickness 0.70; Height 5.50 Capacitors, Polarized Axial Diameter Horizontal Mounting................CAPPA + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: CAPPAD800W52L600D150BCapacitors, Polarized Axial Diameter; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Capacitor, Polarized Radial Diameter.................................................CAPPR + Lead Spacing + W Lead Width + D Body Diameter + H Body Height Example: CAPPRD200W52D300H550BCapacitors, Polarized Radial Diameter; lead spacing 2.00; lead width 0.52; Body Diameter 3.00; Height 5.50Diodes, Axial Diameter Horizontal Mounting.......................................DIOAD + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: DIOAD800W52L600D150BCapacitors, Non Polarized Axial Diameter; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Diodes, Axial Diameter Vertical Mounting .........................................DIOADV + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: DIOADV300W52L600D150BCapacitors, Non Polarized Axial; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Dual-In-Line Packages...................................DIP + Lead Span + W Lead Width + P Pin Pitch + L Body Length + H Component Height + Q Pin Qty Example: DIP762W52P254L1905H508Q14BDual-In-Line Package: Lead Span 7.62; Lead Width 0.52; Pin Pitch 2.54; Body Length 19.05; Body Height 5.08; Pin Qty 14Component, Category Land Pattern Name Dual-In-Line Sockets....................................DIPS + Lead Span + W Lead Width + P Pin Pitch + L Body Length + H Component Height + Q Pin Qty Example: DIPS762W52P254L1905H508Q14BDual-In-Line Package Socket: Lead Span 7.62; Lead Width 0.52; Pin Pitch 2.54; Body Length 19.05; Body Height 5.08; Pin Qty 14Headers, Vertical....... HDRV + Lead Span + W Lead Width + P Pin Pitch + R Pins per Row + L Body Length + T Body Thickness + H Component HeightExample: HDRV200W52P200R2L4400T400H900BHeader, Vertical: Lead Span 2.00; Lead Width 0.52; Pin Pitch 2.00; 2 Rows; Body Length 44.00; Body Thickness 4.00; Body Height 9.00 Headers, Right Angle...............HDRRA + Lead Span + W Lead Width + P Pin Pitch + R Pins per Row + L Body Length + T Body Thickness + H Component HeightExample: HDRRA200W52P200R2L4400T400H900BHeader, Vertical: Lead Span 2.00; Lead Width 0.52; Pin Pitch 2.00; 2 Rows; Body Length 44.00; Body Thickness 4.00; Body Height 9.00 Inductors, Axial Diameter Horizontal Mounting....................................INDAD + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: INDAD800W52L600D150BInductors, Axial Diameter; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Inductors, Axial Diameter Vertical Mounting .....................................INDADV + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: INDADV300W52L600D150BInductors, Axial Diameter Vertical Mounting; Lead Spacing 3.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Jumpers, Wire...................................................................................................................................................JUMP + Lead Spacing + W Lead Width Example: JUMP500W52BJumper; Lead Spacing 5.00; Lead Width 0.52Mounting Holes Plated With Support Pad..........................................................................MTGP + Pad Size + H Hole Size + Z Inner Layer Pad Size Example: MTGP700H400Z520This is a Mounting hole for a #6-32 screw using a circular 7.00 land on the primary and secondary side of the board, a 4.00 diameter hole with the internal lands are smaller that the external and are also circular 5.20 in diameter.Mounting Holes Non-Plated With Support Pad................................................................MTGNP + Pad Size + H Hole Size + Z Inner Layer Pad Size Example: MTGNP700H400Z520This is a Mounting hole for a #6-32 screw using a circular 7.00 land on the primary and secondary side of the board, a 4.00 diameter hole with the internal lands are smaller that the external and are also circular 5.20 in diameter.Mounting Holes Non-Plated Without Support Pad.....................MTGNP + Pad Size + H Hole Size + Z Inner Layer Pad Size + K Keep-out Diameter Example: MTGNP100H400Z520K700This is a Mounting hole for a #6-32 screw using a circular 1mm land on the primary and secondary side of the board, a 4.00 diameter hole with the internal lands are smaller that the external and are also circular 5.20 in diameter and a 7.00 diameter keep-out.Mounting Holes Plated with 8 Vias .....................................................................MTGP + Pad Size + H Hole Size + Z Inner Layer Pad Size + 8 Vias Example: MTGP700H400Z520V8This is a Mounting hole for a #6-32 screw using a circular 7mm land on the primary and secondary side of the board, a 4mm diameter hole with the internal lands are smaller that the external and are also circular 5.2mm in diameter, with 8 vias.Pin Grid Array’s.............................PGA + Pin Qty + P Pitch + C Pin Columns + R Pin Rows + L Body Length X Body Width + H Component Height Example: PGA84P254C10R10L2500X2500H300BPin Grid Array: Pin Qty 84; Pin Pitch 2.54; Columns 10; Rows 10; Body Length 25.00 X 25.00; Component Height 3.00Resistors, Axial Diameter Horizontal Mounting...................................RESAD + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: RESAD800W52L600D150BResistors, Axial Diameter; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Resistors, Axial Diameter Vertical Mounting ....................................RESADV + Lead Spacing + W Lead Width + L Body Length + D Body Diameter Example: RESADV300W52L600D150BResistors, Axial Diameter Vertical Mounting; Lead Spacing 3.00; Lead Width 0.52; Body Length 6.00; Body Diameter 1.50Resistors, Axial Rectangular Horizontal Mounting...RESAR + Lead Spacing + W Lead Width + L Body Length + T Body thickness + H Body Height Example: RESAR800W52L600T50H70BResistors, Axial Rectangular; Lead Spacing 8.00; Lead Width 0.52; Body Length 6.00; Body Thickness 0.50; Body Height 0.70Test Points, Round Land......................................................................................................................................................................TP + Lead Width Example: TP52Test Points, Square Land..................................................................................................................................................................TPS + Lead Width Example: TPS52Test Points, Top Land Round & Bottom Land Square.....................................................................................................................TPRS + Lead Width Example: TPRS52 Wire....................................................................................................................................................................................................PAD + Wire Width Example: PAD52。

Oracle删除和重建由primary约束建立的索引

Oracle 删除和重建由primary 约束建立的索引drop index时出现如下错误：SQL> drop index oos_index;drop index oos_indexERROR at line 1:ORA-02429: cannot drop index used for enforcement ofunique/primary key我们知道当创建Primary key和unique约束时，如果在该key上不存在索引，则Oracle会自动创建对应的unique索引，而当你要删除该索引时，必须先Disable或Drop该约束。

看下面的例子：SQL>CREATE TABLE employees2 (3 empno NUMBER(6) PRIMARY KEY,4 name VARCHAR2(30),5 dept_no NUMBER(2)6 );Table created.SQL> select index_name,owner,table_NAME from all_indexes where owner=’SFA’ AND table_name=’EMPLOYEES’;INDEX_NAME OWNER TABLE_NAME———————- ——————- —————–SYS_C007594 SFA EMPLOYEESSQL> SELECTCONSTRAINT_NAME,CONSTRAINT_TYPE,TABLE_NAME,INDE X_NAME FROM ALL_CONSTRAINTS WHERETABLE_NAME=’EMPLOYEES’;CONSTRAINT_NAME C TABLE_NAME INDEX_NAME ———————————————————- ——————SYS_C007594 P EMPLOYEES SYS_C007594SQL> DROP INDEX SYS_C007594;DROP INDEX SYS_C007594*ERROR at line 1:ORA-02429: cannot drop index used for enforcement ofunique/primary keySQL> ALTER TABLE employees MODIFY PRIMARY KEY DISABLE;Table altered.SQL> select index_name,owner,table_NAME from all_indexes where owner=’SFA’ AND table_name=’EMPLOYEES’;no rows selected这时看到由约束建立的索引已经删除了。

MySQL约束详解

MySQL约束详解MySQL 约束详解MySQL 中的约束是⽤来保证数据的完整性的机制。

数据完整性⼀般有以下三种形式：1. 实体完整性：保证表中有⼀个主键。

2. 域完整性：保证数据每列的值满⾜特定条件。

3. 引⽤完整性：保证两张表之间的引⽤关系。

以上三种形式的完整性在 MySQL 中都有相应约束进⾏保证。

使⽤主键和唯⼀键约束可以保证实体完整性；使⽤外键、合适和数据类型、触发器或者 DEFAULT 关键字也可以保证域完整性；使⽤外键和触发器可以保证引⽤完整性。

可见 MySQL 提供了以下⼏种约束：1. Primary Key2. Unique Key3. Foreign Key4. Default5. NOT NULL6. 触发器Primary key、Unique Key 和 Foreign Key 约束Primary Key ⽤于约束唯⼀主键，唯⼀标识表中的每⼀条记录，主键对应的列不允许有 NULL 值和重复值，每个表都应该只有⼀个主键（包含 Unique 约束）。

Unique Key ⽤于约束唯⼀索引，唯⼀标识表中的每⼀条记录，与 Primary Key 的区别在于可以有多个列同时被定义为 Unique Key。

Foreign Key ⽤于保证域和参照的完整性。

外键当中出现的值必须在其他表中为主键。

同时当⽗表发⽣变化时，对⼦表的操作可以有 4 种⽅案：CASCADE（删除⼦表对应的⾏）、SET NULL（将⼦表对应⾏置空）、NO ACTION、RESTRICT。

对错误数据的约束MySQL 允许⾮法的或不正确的数据的插⼊或更新，例如向 NOT NULL 的列中插⼊⼀个 NULL 值，那么此时 MySQL 会将 NULL 值更改为 0值插⼊。

如果想要 MySQL 在⽤户插⼊错误数据时进⾏报错⽽不是警告，需要设置参数 sql_mode。

ENUM 和 SET 约束⽤来约束离散值在⼀个集合以内。

如果是连续值和范围的约束需要通过触发器去实现。

primary_sample_unit_介绍_概述及解释说明

primary sample unit 介绍概述及解释说明1. 引言1.1 概述在统计学中，抽样是收集和分析数据的重要方法之一。

而"primary sample unit"（以下简称PSU）作为抽样设计的基本单位，在实施调查和研究中扮演着至关重要的角色。

本文旨在对PSU进行介绍、概述并进行解释说明，以便更好地理解其定义、应用及相关概念。

1.2 文章结构本文将主要包括以下几个部分：引言、主体部分、解释说明、结论和参考文献。

其中，主体部分将详细探讨PSU的定义、背景介绍、重要性与应用、组成要素与特征等方面内容。

而在解释说明部分，我们将着重讲解PSU在统计学中的作用和意义，同时与其他抽样方法进行比较，并提供如何选择合适的PSU以提高数据的代表性和可靠性的建议。

1.3 目的通过本文，旨在明确阐述以下几点目标：- 提供一个清晰准确的定义给出什么是"primary sample unit"；- 探索PSU在实际调查和研究中的重要性及应用领域；- 解析PSU所包含的组成要素与特征；- 分析PSU在统计学中的作用和意义；- 比较PSU与其他抽样方法的优劣；- 提供如何选择合适的PSU以提高数据代表性和可靠性的建议。

在阅读完本文后，读者将能够更加全面地了解并掌握PSU这一概念及其相关内容，以及在实际应用中做出明智的决策。

2. 主体部分：2.1 primary sample unit 定义与背景介绍在统计学中，primary sample unit（PSU）是指进行抽样的最小单位。

它可以是一个人、一户、一个街区或者其他具有独特特征的单元。

PSU被用来代表总体中的个体，并从中收集数据以进行进一步的分析。

PSU的选择需要根据研究目的和样本要求确定。

在实际应用中，PSU通常是由相邻个体或单元组成的群体。

例如，在人口普查调查中，一个街区可以作为一个PSU；在市场调研中，一个家庭可以被视为一个PSU。

单复同形

名词单复数的讲解！！1.不规则复数形式1）来自古英语的复数形式，如：child---childrenfoot---feettooth---teethgoose---geeselouse---licemouse---micewoman---womenman---menox---oxenpenny---penceappendix---appendices analysis---analyses parenthesis---parentheses basis---basesellipsis---ellipsescrisis----criseshypothesis---hypotheses axis---axesoasis---oasesdatum---data phenomenon---phenomena criterion---criteriamedium---media bacterium---bacteria nucleus---nucleifungus---fungistimulus---stimulialumnus---alumnilarva---larvaefocus---fociradius---radiiterminus---terminialga---algaeformula---formulae当代美国英语中往往把d a t a当做单数用，因此常见到复数形式datas。

另外，l e n s是一个单数可数名词，其复数形式为lenses。

1）词尾读音为[f]并以－f或a）规则形式：belief---beliefschief----chiefscliff----cliffsgrief----griefsb）不规则形式，即把－f或－f e变成－v，再加－e s,读音为[v z]:calf---calveshalf---halvesleaf----le ave slife----livesloaf---loavesself---shel ve sthief---thieveswife---wiveswolf---wolvesc）既可是规则形式又可是不规则形式：dwarf---dwarfs/dwarveshoof---hoofs/hovesscarf---scarfs/s c a r v e swharf---wharfs/wharves3）词干以－o结尾的名次有三种情况：a）附属形式为－s：这类词包括缩略词kilos, photos；表示国籍或民族的词Filipinos, Eskimos以及radios, solos, sopranos, studiosb）复数形式为－e s，如：heroes, potatoes, tomatoes, Negroes。

CREATETABLE语句后的ON[PRIMARY]起什么作用

CREATETABLE语句后的ON[PRIMARY]起什么作⽤CREATE TABLE [dbo].[table1] ([gh] [char] (10) COLLATE Chinese_PRC_CI_AS NOT NULL PRIMARY KEY ,[gh2] [char] (10) COLLATE Chinese_PRC_CI_AS NULL) ON [PRIMARY]⽐如以上创建表的语句，不知最后的 ON [PRIMARY] 起何⽤？没有也⾏呀，为什么？------解决⽅案--------------------指定存储表的⽂件组。

如果指定 filegroup，则表将存储在指定的⽂件组中。

数据库中必须存在该⽂件组。

如果指定 DEFAULT，或者根本未指定 ON 参数，则表存储在默认⽂件组中。

ON {filegroup | DEFAULT} 也可以在 PRIMARY KEY 约束或 UNIQUE 约束中指定。

这些约束会创建索引。

如果指定 filegroup，则索引将存储在指定的⽂件组中。

如果指定 DEFAULT，则索引将存储在默认⽂件组中。

如果约束中没有指定⽂件组，则索引将与表存储在同⼀⽂件组中。

如果 PRIMARY KEY 约束或 UNIQUE 约束创建聚集索引，则表的数据页将与索引存储在同⼀⽂件组中。

------解决⽅案--------------------创建⽂件组在⾸次创建数据库，或者以后将更多⽂件添加到数据库时，可以创建⽂件组。

但是，⼀旦将⽂件添加到数据库，就不可能再将这些⽂件移到其它⽂件组。

⼀个⽂件不能是多个⽂件组的成员。

表格、索引以及 text、ntext 和 image 数据可以与特定的⽂件组相关联。

这意味着它们的所有页都将从该⽂件组的⽂件中分配。

有三种类型的⽂件组：主⽂件组这些⽂件组包含主数据⽂件以及任何其它没有放⼊其它⽂件组的⽂件。

系统表的所有页都从主⽂件组分配。

⽤户定义⽂件组该⽂件组是⽤ CREATE DATABASE 或 ALTER DATABASE 语句中的 FILEGROUP 关键字，或在 SQL Server 企业管理器内的 "属性 "对话框上指定的任何⽂件组。

这几个神秘参数，教你TDengine集群的正确使用方式

这⼏个神秘参数，教你TDengine集群的正确使⽤⽅式⼩ T 导读：为什么我的集群数据分布得不均匀？这篇⽂章就是为了解决这个问题⽽写的。

但即便是没有遇到“TDengine集群数据不均匀分布”这个现象的⽤户，我们也推荐⼀读。

因为可能你⽬前只是在通⽤场景下使⽤集群，当⼀些特殊的场景出现时，深⼊地了解集群参数和数据库架构原理才会真正地让你做到游刃有余。

⾄于集群如何搭建并不是本⽂主题，请严格根据官⽅⽂档指⽰操作即可。

官⽅⽂档地址：为了充分理解⽂章内容，⾸先⼤家⼀定要先了解vnode这个概念——每个 vnode 都是⼀个相对独⽴的⼯作单元，是存储时序数据（表）的基本单元，具有独⽴的运⾏线程，内存空间与持久化存储的路径。

如果觉得不够清晰的话，接着往下读，随着知识点的串联，或许您会豁然开朗起来。

现在，我们来根据不同的场景给出具体分析：通常来说，数据分配不均匀有两种。

场景⼀：表分布不均匀需要测试表数量很少的数据库性能时⽐较容易发⽣这个现象：你建了1200张表，但是却发现有1000张表都在同⼀个vnode⾥⾯，只有200张表在另⼀个vnode⾥⾯。

这种场景的坏处是，⼤部分表都进⼊了同⼀个vnode数据分布不均匀。

此外还会导致只有两个线程在为TDengine⼯作，因此⽆法利⽤计算机的多核（假设你的服务器CPU是双核以上），从⽽浪费了TDengine的横向扩展性。

我先来简单说说导致上述情况的原因——在TDengine中有这样三个参数：maxVgroupsPerDb: 每个数据库中能够使⽤的最⼤vnode个数（单个副本），默认为0；minTablesPerVnode: 每个vnode中必须创建的最⼩表数，即是说这是第⼀轮建表⽤的步长（就是满多少表写下⼀个vnode），默认1000；tablelncStepPerVnode：每个vnode中超过最⼩表数后的递增步长（即是后续满多少表写下⼀个vnode），默认1000。

在持续的建表过程中，TDengine就是靠这三个参数来控制表的分布的。