A Graph Query Language and its Query Processing
graph matching problem：图匹配问题
…
Biology data Documents Program flow
Image
2021/4/26
SOC@NUS
4
Thesis defense by Xiaoli Wang
Real application: social reading systems
Book duplicate detection problem
GED bound computation
GED computation
candidates
100,000
5% scan
100
index
answers 50
Inverted index based on the star decomposition The graph is decomposed into smaller stars Inverted index is designed to store the reference between graphs and stars Efficient CA-based search framework is proposed
2021/4/26
SOC@NUS
9
Thesis defense by Xiaoli Wang
Objectives
Building a 3-in-1 unified indexing system Design a unified and effective indexing mechanism Support similarity search on various complex structures
Waste resource to re-design various storage systems
sql 考试题
好的，以下是一份简单的SQL考试题，包括选择题和简答题。
一、选择题
1. SQL的全称是什么？
A. Structured Query Language
B. Standard Query Language
C. Server Query Language
D. Simple Query Language
2. 在SQL中，哪个关键字用于选择所有列？
A. SELECT
B. FROM
C. WHERE
D. ALL
3. 哪个关键字用于在SQL查询中添加过滤条件？
A. WHERE
B. AND
C. OR
D. NOT
4. 在SQL中，哪个关键字用于排序查询结果？
A. ORDER BY
B. GROUP BY
C. HAVING
D. JOIN
5. 在SQL中，哪个关键字用于指定多表连接的类型？
A. JOIN
B. ON
C. WHERE
D. ORDER BY
二、简答题
1. 描述在SQL中如何使用`JOIN`关键字连接两个表，并指定连接条件。
2. 解释`SELECT`语句的作用，并给出一个简单的`SELECT`语句的例子。
3. 描述在SQL中如何使用`WHERE`子句对查询结果进行过滤。
4. 解释在SQL中如何使用`GROUP BY`子句对结果进行分组。
5. 描述在SQL中如何使用`ORDER BY`子句对查询结果进行排序。
数据库线上考试题目及答案
数据库线上考试题目及答案一、选择题（每题2分，共20分）1. 数据库管理系统（DBMS）的主要功能是什么？A. 存储数据B. 管理数据C. 提供数据访问接口D. 所有选项都是答案：D2. 关系数据库中的主键约束用于保证数据的什么特性？A. 唯一性B. 完整性C. 一致性D. 可扩展性答案：A3. SQL（Structured Query Language）是一种用于什么的语言？A. 数据查询B. 数据定义C. 数据操纵D. 所有选项都是答案：D4. 在关系数据库中，一个表的行通常被称为什么？A. 字段B. 记录C. 索引D. 视图答案：B5. 数据库规范化的主要目的是什么？A. 提高查询速度B. 减少数据冗余C. 增加数据安全性D. 降低存储成本答案：B二、填空题（每空1分，共10分）6. 数据库中的_______用于定义数据表的结构。
答案：模式（Schema）7. 在SQL中，用于添加数据的命令是_______。
答案：INSERT8. 数据库事务的四大特性通常被称为ACID，其中C代表_______。
答案：一致性（Consistency）9. 在数据库中，_______用于优化查询性能。
答案：索引（Index）10. 数据库备份的目的是_______。
答案：数据恢复三、简答题（每题10分，共20分）11. 简述数据库的三级模式结构。
答案：数据库的三级模式结构包括外模式（External Schema）、概念模式（Conceptual Schema）和内模式（Internal Schema）。
外模式是用户视图，描述用户需要的数据；概念模式是全局视图，描述数据库的整体结构；内模式是存储视图，描述数据的物理存储方式。
12. 什么是数据库的并发控制，为什么它很重要？答案：数据库的并发控制是确保多个用户或应用程序能够同时访问数据库，而不会导致数据不一致或错误的一种机制。
它很重要，因为并发控制可以防止诸如脏读、不可重复读和幻读等问题，确保数据库的完整性和一致性。
Neo4j教程：基础到高级概念说明书
About the T utorialNeo4j is one of the popular Graph Databases and Cypher Query Language (CQL). Neo4j is written in Java Language. This tutorial explains the basics of Neo4j, Java with Neo4j, and Spring DATA with Neo4j.The tutorial is divided into sections such as Neo4j Introduction, Neo4j CQL, Neo4j CQL Functions, Neo4j Admin, etc. Each of these sections contain related topics with simple and useful examples.AudienceThis tutorial has been prepared for beginners to help them understand the basic to advanced concepts of Neo4j. It will give you enough understanding on Neo4j from where you can take yourself to a higher level of expertise.PrerequisitesBefore proceeding with this tutorial, you should have basic knowledge of Database, Graph Theory, Java, and Spring Framework.Copyright & Disclaimer© Copyright 2018 by Tutorials Point (I) Pvt. Ltd.All the content and graphics published in this e-book are the property of Tutorials Point (I) Pvt. Ltd. The user of this e-book is prohibited to reuse, retain, copy, distribute or republish any contents or a part of contents of this e-book in any manner without written consent of the publisher.We strive to update the contents of our website and tutorials as timely and as precisely as possible, however, the contents may contain inaccuracies or errors. Tutorials Point (I) Pvt. Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of our website or its contents including this tutorial. If you discover any errors on our website or in this tutorial, please notify us at **************************T able of ContentsAbout the Tutorial (i)Audience (i)Prerequisites (i)Copyright & Disclaimer (i)Table of Contents (ii)1.Neo4j ─ Overview (1)What is a Graph Database? (1)Advantages of Neo4j (2)Features of Neo4j (2)2.Neo4j ─ Data Model (4)3.Neo4j ─ Environment Setup (6)Neo4j Database Server Setup with Windows exe File (6)Starting the Server (9)Working with Neo4j (11)4.Neo4j ─ Building Blocks (12)Node (12)Properties (12)Relationships (13)Labels (14)Neo4j Data Browser (14)NEO4J ─ CQL (17)5.Neo4j CQL ─ I ntroduction (18)Neo4j CQL Clauses (18)Neo4j CQL Functions (20)Neo4j CQL Data Types (21)CQL Operators (21)Boolean Operators in Neo4j CQL (22)Comparison Operators in Neo4j CQL (22)6.Neo4j CQL ─ Creating Nodes (24)Creating a Single node (24)Creating Multiple Nodes (27)Creating a Node with a Label (30)Creating a Node with Multiple Labels (33)Create Node with Properties (36)Returning the Created Node (39)7.Neo4j CQL ─ Creating a Relationship (42)Creating Relationships (42)Creating a Relationship Between the Existing Nodes (44)Creating a Relationship with Label and Properties (47)Creating a Complete Path (49)N EO4J CQL ─ WRITE CLA USES (51)8.Neo4j ─ Merge Command (52)Merging a Node with a Label (52)Merging a Node with Properties (56)OnCreate and OnMatch (58)Merge a Relationship (61)9.Neo4j ─ Set Clause (63)Setting a Property (63)Removing a Property (65)Setting Multiple Properties (67)Setting a Label on a Node (69)Setting Multiple Labels on a Node (71)10.Neo4j ─ Delete Clause (74)Deleting All Nodes and Relationships (74)Deleting a Particular Node (75)11.Neo4j ─ Remove Clause (77)Removing a Property (77)Removing a Label From a Node (79)Removing Multiple Labels (81)12.Neo4j ─ Foreach Clause (84)NEO4J CQL ─ READ CLA USES (87)13.Neo4j ─ Match Clause (88)Get All Nodes Using Match (88)Getting All Nodes Under a Specific Label (90)Match by Relationship (92)Delete All Nodes (94)14.Neo4j ─ Optional Match Clause (96)15.Neo4j ─ Where Clause (98)WHERE Clause with Multiple Conditions (101)Using Relationship with Where Clause (103)16.Neo4j ─ Count Function (106)Count (106)Group Count (108)N EO4J CQL ─ GENERAL C LAUSES (111)17.Neo4j ─ Return Clause (112)Returning Nodes (112)Returning Multiple Nodes (114)Returning Relationships (116)Returning Properties (118)Returning All Elements (120)Returning a Variable With a Column Alias (122)18.Neo4j ─ Order By Clause (124)Ordering Nodes by Multiple Properties (126)Ordering Nodes by Descending Order (128)19.Neo4j ─ Limit Clause (131)Limit with expression (133)20.Neo4j ─ Skip Clause (136)Skip Using Expression (138)21.Neo4j ─ With Clause (140)22.Neo4j ─ Unwind Clause (142)NE O4J CQL ─ FUNCTIONS (144)23.Neo4J CQL ─ String Functions (145)String Functions List (145)Upper (145)Lower (147)Substring (149)24.Neo4j ─ Aggreg ation Function (152)AGGREGATION Functions List (152)COUNT (152)MAX (155)MIN (157)AVG (159)SUM (161)N EO4J CQL ─ ADMIN (163)25.Neo4j ─ Backup & Restore (164)Neo4j Database Backup (164)Neo4j Database Restore (171)26.Neo4j ─ Index (174)Creating an Index (174)Deleting an Index (176)27.Neo4j ─ Create Unique Constraint (179)Create UNIQUE Constraint (179)28.Neo4j ─ Drop Unique (182)Neo4j5Neo4j is the world's leading open source Graph Database which is developed using Java technology. It is highly scalable and schema free (NoSQL).What is a Graph Database?A graph is a pictorial representation of a set of objects where some pairs of objects are connected by links . It is composed of two elements - nodes (vertices) and relationships (edges).Graph database is a database used to model the data in the form of graph. In here, the nodes of a graph depict the entities while the relationships depict the association of these nodes. Popular Graph DatabasesNeo4j is a popular Graph Database. Other Graph Databases are Oracle NoSQL Database, OrientDB, HypherGraphDB, GraphBase, InfiniteGraph, and AllegroGraph.Why Graph Databases?Nowadays, most of the data exists in the form of the relationship between different objects and more often, the relationship between the data is more valuable than the data itself.Relational databases store highly structured data which have several records storing the same type of data so they can be used to store structured data and, they do not store the relationships between the data.Unlike other databases, graph databases store relationships and connections as first-class entities.The data model for graph databases is simpler compared to other databases and, they can be used with OLTP systems. They provide features like transactional integrity and operational availability.RDBMS Vs Graph DatabaseFollowing is the table which compares Relational databases and Graph databases.1.Advantages of Neo4jFollowing are the advantages of Neo4j.∙Flexible data model: Neo4j provides a flexible simple and yet powerful data model, which can be easily changed according to the applications and industries.∙Real-time insights: Neo4j provides results based on real-time data.∙High availability: Neo4j is highly available for large enterprise real-time applications with transactional guarantees.∙Connected and semi structures data:Using Neo4j, you can easily represent connected and semi-structured data.∙Easy retrieval: Using Neo4j, you can not only represent but also easily retrieve (traverse/navigate) connected data faster when compared to other databases.∙Cypher query language: Neo4j provides a declarative query language to represent the graph visually, using an ascii-art syntax. The commands of this language are in human readable format and very easy to learn.∙No joins: Using Neo4j, it does NOT require complex joins to retrieve connected/related data as it is very easy to retrieve its adjacent node or relationship details without joins or indexes.Features of Neo4jFollowing are the notable features of Neo4j -∙Data model (flexible schema): Neo4j follows a data model named native property graph model. Here, the graph contains nodes (entities) and these nodes are connected with each other (depicted by relationships). Nodes and relationships store data in key-value pairs known as properties.In Neo4j, there is no need to follow a fixed schema. You can add or remove properties as per requirement. It also provides schema constraints.6∙ACID properties: Neo4j supports full ACID (Atomicity, Consistency, Isolation, and Durability) rules.∙Scalability and reliability: You can scale the database by increasing the number of reads/writes, and the volume without effecting the query processing speed and data integrity. Neo4j also provides support for replication for data safety and reliability.∙Cypher Query Language: Neo4j provides a powerful declarative query language known as Cypher. It uses ASCII-art for depicting graphs. Cypher is easy to learn and can be used to create and retrieve relations between data without using the complex queries like Joins.∙Built-in web application: Neo4j provides a built-in Neo4j Browser web application.Using this, you can create and query your graph data.∙Drivers: Neo4j can work with –o REST API to work with programming languages such as Java, Spring, Scala etc.o Java Script to work with UI MVC frameworks such as Node JS.o It supports two kinds of Java API: Cypher API and Native Java API to develop Java applications.In addition to these, you can also work with other databases such as MongoDB, Cassandra, etc.∙Indexing: Neo4j supports Indexes by using Apache Lucence.7Neo4j8Neo4j Property Graph Data ModelNeo4j Graph Database follows the Property Graph Model to store and manage its data. Following are the key features of Property Graph Model:∙The model represents data in Nodes, Relationships and Properties ∙Properties are key-value pairs ∙ Nodes are represented using circle and Relationships are represented using arrow keys ∙Relationships have directions: Unidirectional and Bidirectional ∙ Each Relationship contains "Start Node" or "From Node" and "To Node" or "End Node" ∙Both Nodes and Relationships contain properties ∙ Relationships connects nodesIn Property Graph Data Model, relationships should be directional. If we try to create relationships without direction, then it will throw an error message.In Neo4j too, relationships should be directional. If we try to create relationships without direction, then Neo4j will throw an error message saying that "Relationships should be directional".Neo4j Graph Database stores all of its data in Nodes and Relationships. We neither need any additional RRBMS Database nor any SQL database to store Neo4j database data. It stores its data in terms of Graphs in its native format.Neo4j uses Native GPE (Graph Processing Engine) to work with its Native graph storage format.The main building blocks of Graph DB Data Model are:∙Nodes ∙Relationships ∙Properties2.Neo4j Following is a simple example of a Property Graph.Here, we have represented Nodes using Circles. Relationships are represented using Arrows. Relationships are directional. We can represent Node's data in terms of Properties (key-value pairs). In this example, we have represented each Node's Id property within the Node's Circle.9Neo4j10In this chapter, we will discuss how to install Neo4j in your system using exe file.Neo4j Database Server Setup with Windows exe FileFollow the steps given below to download Neo4j into your system.Step 1: Visit the Neo4j official site using https:///. On clicking, this link will take you to the homepage of neo4j website.Step 2: As highlighted in the above screenshot, this page has a Download button on the top right hand side. Click it.Step 3: This will redirect you to the downloads page, where you can download the community edition and the enterprise edition of Neo4j. Download the community edition of the software by clicking the respective button.3.Step 4: This will take you to the page where you can download community version of Neo4j software compatible with different operating systems. Download the file respective to the desired operating system.11This will download a file named neo4j-community_windows-x64_3_1_1.exe to your system as shown in the following screenshot.12Step 5: Double-click the exe file to install Neo4j Server.Step 6: Accept the license agreement and proceed with the installation. After completion of the process, you can observe that Neo4j is installed in your system.Starting the ServerStep 1: Click the Windows startmenu and start the Neo4j server by clicking the start menu shortcut for Neo4j.13Step 2: On clicking the shortcut, you will get a window for Neo4j Community edition. By default, it selects c:\Users\[username]\Documents\Neo4j\default.graphdb. If you want, you can change your path to a different directory.14Step 3: Click the "Start" button to start the Neo4j server.Once the server starts, you can observe that the database directory is populated as shown in the following screenshot.15Working with Neo4jAs discussed in the previous chapters, neo4j provides an in-built browse application to work with Neo4j. You can access Neo4j using the URL http://localhost:7474/16Neo4j17Neo4j Graph Database has the following building blocks -∙ Nodes ∙ Properties ∙ Relationships ∙ Labels ∙Data BrowserNodeNode is a fundamental unit of a Graph. It contains properties with key-value pairs as shown in the following image.Here, Node Name = "Employee" and it contains a set of properties as key-value pairs.4.PropertiesProperty is a key-value pair to describe Graph Nodes and Relationships.Where Key is a String and Value may be represented using any Neo4j Data types.RelationshipsRelationships are another major building block of a Graph Database. It connects two nodes as depicted in the following figure.Here, Emp and Dept are two different nodes. "WORKS_FOR" is a relationship between Emp and Dept nodes.As it denotes, the arrow mark from Emp to Dept, this relationship describes -Each relationship contains one start node and one end node.Here, "Emp" is a start node, and "Dept" is an end node.As this relationship arrow mark represents a relationship from "Emp" node to "Dept" node, this relationship is known as an "Incoming Relationship" to "Dept" Node and "Outgoing Relationship" to "Emp" node.Like nodes, relationships also can contain properties as key-value pairs.18Here, "WORKS_FOR" relationship has one property as key-value pair.It represents an Id of this relationship.LabelsLabel associates a common name to a set of nodes or relationships. A node or relationship can contain one or more labels. We can create new labels to existing nodes or relationships. We can remove the existing labels from the existing nodes or relationships.From the previous diagram, we can observe that there are two nodes.Left side node has a Label: "Emp" and the right side node has a Label: "Dept". Relationship between those two nodes also has a Label: "WORKS_FOR".Note: Neo4j stores data in Properties of Nodes or Relationships.Neo4j Data BrowserOnce we install Neo4j, we can access Neo4j Data Browser using the following URL19Neo4j Data Browser is used to execute CQL commands and view the output.Here, we need to execute all CQL commands at dollar prompt: "$"Type commands after the dollar symbol and click the "Execute" button to run your commands. It interacts with Neo4j Database Server, retrieves and displays the results just below the dollar prompt.Use "VI View" button to view the results in diagrams format. The above diagram shows results in "UI View" format.Use "Grid View" button to view the results in Grid View. The following diagram shows the same results in "Grid View" format.20When we use "Grid View" to view our Query results, we can export them into a file in two different formats.21CSVClick the "Export CSV" button to export the results in csv file format.JSONClick the "Export JSON" button to export the results in JSON file format.22However, if we use "UI View" to see our Query results, we can export them into a file in only one format: JSON23Neo4j ─ CQL24Neo4j25CQL stands for Cypher Query Language. Like Oracle Database has query language SQL, Neo4j has CQL as query language.Neo4j CQL -∙ Is a query language for Neo4j Graph Database. ∙ Is a declarative pattern-matching language. ∙ Follows SQL like syntax.∙Syntax is very simple and in human readable format.Like Oracle SQL -∙ Neo4j CQL has commands to perform Database operations.∙Neo4j CQL supports many clauses such as WHERE, ORDER BY, etc., to write very complex queries in an easy manner.∙Neo4j CQL supports some functions such as String, Aggregation. In addition to them, it also supports some Relationship Functions.Neo4j CQL ClausesFollowing are the read clauses of Neo4j C ypher Q uery L anguage: 5.Following are the write clauses of Neo4j C ypher Q uery L anguage:Following are the general clauses of Neo4j C ypher Q uery L anguage:26Neo4j CQL FunctionsFollowing are the frequently used Neo4j CQL Functions:We will discuss all Neo4j CQL commands, clauses and functions syntax, usage and examples in-detail in the subsequent chapters.27End of ebook previewIf you liked what you saw…Buy it from our store @ https://28。
SQL_Server简介外文翻译
外文原文Introduction to SQL ServerBy SamuelRelational databases have been around for 30 years, but they were not the original kind ofdatabase, nor are they the newest kind of database. XML and object-oriented data structures haveevolved in recent years. But relational databases are still by far the most popular kind of database available and will be for some time to come.SQL is the abbreviation of Structured Query Language and it is for relational databases, as the title indicates this is only for fresher who has just started the carrier or who is waiting to open up the carrier in the application programming side. But that does not mean this article is a tutorial for a fresher who does not know anything about SQL.This article is meant for who already have a little knowledge in SQL and want toimprove it.What Does SQL Do?F irst, SQL is the premier tool for viewing information from a relational database. It doesn’t just give you a data dump. SQL gives you sophisticated tools to summarize, consolidate, and calculate from the data. Using table relationships, data can be combined from multiple tables in a number of ways. With a properly designed database, SQL can answer practically any question about the data.Second, SQL provides commands to manipulate the data in a relational database. Records can be updated and added to or deleted from a table. Here is SQL as a database language really shines. Procedural programming languages, such as BASIC, might require several lines of code to update a record in a database table. In addition, procedural programming languages would have to use some sort of looping structure to repeat this process on every record. SQL operates on an entire set of records all at the same time. SQL is like haiku for programmers; often a dozen words or fewer can delete or change thousands of records.Finally, SQL is a complete data definition language (DDL). The database itself can be created along with all tables, fields, primary keys, and relationships. Add to that the record insert commands, and you can have a complete database and all its data expressed in programming code. This greatly enhances a database programmer’s ability to work remotely or to port data enhancements among various installations.The prerequisite for learning SQL is knowledge in Discrete Mathematics (Set Theory,Relations and Functions). Although it is not necessary to learn all the theorems and proof for the theorems in the Discrete Mathematics, you should have learned the basicconcepts of the Sets, Relations and Functions. This will help you to learn SQL queries and fundamentals easily. If you want to explore a RDBMS more deeply you should learn Graph Theory too.Although I tried to avoid SQL Server specific topics in this article, I am sure that some topics are pure to SQL server such as SQL Enterprise manager.Data to DBMSData is something that should be stored for future manipulations (In terms of Database). The system which provides such a facility is called Database Management System or DBMS.The simplest form to store a data for latter retrieval is using a text file. For example you may want to store your friends name and phone numbers to use it latter. (In this case you may use notepad or word to do so.) This kind of storage is called flat file storage or unstructured storage. In this case the text editor uses the File and Directory services provided by the Operating System to accomplish the task of storing and retrieving data.But these unstructured flat files are not suitable to large data such as storing stock details. Since the stock data is large in volume and added and updated frequently it is not scale up well if we use a simple flat file. To overcome this we need some system which should perform the storing, retrieving, manipulating and querying operations on the data and give output to us. This kind of system is called Database Management System. So a DBMS is a system which organizes and stores data in a structural way for fast retrieval. A DBMS uses one or more files to store the given data.Since the DBMS is meant mainly for developers every DBMS has it is own language to write the commands. The languages are standardized under the name SQL(Structured Query Language). The following definition for SQL is from Books Online“A language used to insert, retrieve, modify, and delete data in a relational database.SQL also contains statements for defining and administering the objects in a database. SQL is the language supported by most relational databases, and is the subject of standards published by the International Standards Organization (ISO)and the American National Standards Institute (ANSI). SQL Server 2000 uses a version of the SQL language called Transact-SQL.”Representation of Data by DBMSDBMS should represent the data stored by them in some form and it is most common to represent them as Column, Row, Tables and Databases. As you know SQL you know what are columns, rows, tables and database.Primary KeyA column or set of columns used to uniquely identify the records in a table. Primary Keys don’t allow NULL va lues. You can relate a table with other table if you have definedprimary on it. (So defining UNIQUE and NOT NULL constraint is not equivalent to primary key). SQL server will create a Clustered index while you create a primary key.Primary keys should be carefully defined since based on it other relations are defined. Poorly designed primary keys will affect insert, update and delete operations. Primary keys are different from which are used for paperwork.Foreign KeyThe primary key of one of the tables is almost always involved in the relationship. The field in the other table on the other end of that relationship is called the foreign key. The term simply refers to the fact that this field is key to relating to a foreign (or other) table. In the Lyric Music database there is a relationship between artists and titles. The ArtistID field is the primary key in the Artists table. Therefore, the ArtistID field in the Titles table is a foreign key. It relates the Titles table to the primary key in the Artists table.Most table relationships can be described as one-to-many. In a one-to-many relationship, a single record in the first table can be related to many records in the second table. However, each record in the second table relates to only one record in the first table. In addition to one-to-many relationship, tables can have one-to-one relationships. But these are much less common.Server – ClientIn Client Server technology, a server is a program which does all the jobs that is requested by the client and Client is a program which depends on the Server to accomplish its task. Client is mainly used to interact with Users and most Server software doesn’t have direct interaction with Users.A DBMS should have the following functionality –Interaction with users (developers),Managing Data. Since these two functionalities are entirely different modern DBMS is divided into two or more parts. Almost all current DBMS has the following module –Server and one or more clients. A server module is program which manages the data and handles requests from the client applications. It interprets the SQL queries and returns results back to the clients. A client program is a program which sends SQL commands to server and gets the result. Client program does not know the detailed underground structure of the server.SQL Server 2000 runs as a service in NT based machines. You have to establish a connection to the server first if you want to do some SQL operation. SQL Server uses Local or Network IPC (Inter process communication) to communicate with the clients. See Books Online for more details.T he most basic misunderstanding of many junior developers is considering SQLEnterprise Manager as the SQL server. SQL Enterprise Manager is a tool used to access the SQL server. SQL Query analyzer is also similar tool used to access the SQL server. The difference between SQL query analyzer and Enterprise Manager is Query Analyzer is a light weight process and Enterprise manager is heavy weight processes due to its Graphical User Interface.Enterprise Manager is a handy tool in the initial stage of a project. It will save lot more time while designing the database. You can easily create Tables, Triggers, Relationships, Constraints etc using Enterprise manger easily. I have seen many of devel opers don’t have experience in using Enterprise Manager. Never become one of them, use Enterprise Manager whenever you start creating a database. Query Analyzer is a tool used to Create, Analyze, Modify and Delete T-SQL queries.You can also access SQL server using osql.exe or isql.exe which is a very light weight command line utility. You can execute T-SQL commands in osql/isql. The difference between osql and isql is osql uses ODBC library whereas isql uses DB library to communicate with the SQL server. SQL Query analyzer is Windows version of isql.exe.You can directly access SQL server by accessing the TCP Port/Named Pipes and issuing certain commands. However it is very tedious, so SQL Server has provided some library to access it easily. You can find the source code for these libraries in the installation directory of the SQL Server. For database communication standards SQL Server fully supports ODBC. Further it has own database driver for communication. SQL Server also offers SQL-DMO (SQL Distributed Management Objects) a COM component which offers easy programming interface. I have created one application called Whiz using the SQL-DMO. You can download source code for that application in my projects page.Apart from these libraries many third party libraries are also available to access SQL Server. In .Net you can directly access SQL server using Data.SQLClient namespace.Now you have learned how SQL Server and SQL Client tools are exists in a network.It is time to learn some Client-Server technology rules1) There may be more than one connection to server at any time2) Client should request only what it wants3) Client requests should be shortThe first point is related to Server so leave it. The second point says that the client should retrieve only the data that it needs. This is because transferring data from Server to Client utilizes server’s resource and also increases network traffic.DDL (Data Definition Language)What is data type? –Classification of data into similar groups. Names, Money,Date,Time, etc are examples for data type.What is the use of classification or data type? – It increases the performance, reduces the space needed to store the data.DML (Data Manipulation Language)Data Manipulation Languages contains command used to query, change, and add data from/to the database. This includes the following commands - SELECT, INSERT, DELETE. All these commands are deals with set of data. So I want to refresh the Set theory concepts before going further.TransactionsA transaction is a sequence of operations performed as a single logical unit of work. A logical unit of work must exhibit four properties, called the ACID (Atomicity, Consistency, Isolation, and Durability) properties, to qualify as a transaction.DTS (Data Transformation Services)Data Transformation Services are used to transfer and transform data from one datasource to another datasoure in the same server or another server.Some applications of DTS1) Copying data from one database to another database2) Copying data structure from one database to another database3) Migrating data from other datasources such as Flat File, Excel, Access, Oracle to SQLServer.4) Migrating data from SQL server to other datasources.Since the DTS topic is huge you cannot get to know what it is until you do actual task that is related to DTS. So try the following things and you will get to know something about DTS. Create an Excel file with the following columns EmployeeName, Address, DateOfJoin, PhoneNumber, MaritialStatus, and Department. Fill this excel sheet with some meaningful information and then try to transfer the contents from Excel to SQL using DTS Import/Export Wizard.You can also create DTS packages which can be scheduled to run at future. DTS package programming allows mapping source fields to different destination fields and also provides error control.SQL ProfilerSQL Profiler is a handy tool used to analyze what is happening inside and outside of a SQL Server. Simply it is a tool which extracts the log information from SQL server.These logs will help you debug applications, optimize queries, redesign database structure.Running SQL Profiler is very easy, Click SQL profiler from the SQL Server group menu.Then select New Trace from the file menu. It will open the connection dialog box. Type your server name, user name and password. Now you have to set options for your profile. The options include what events you want to trace, what columns you want in the output, filters if any.DBCCDatabase Console Commands are referred as DBCC. DBCC contains some special commands through which you can accomplish certain DB operations which is not possible through normal SQL commands.外文翻译SQL server 简介塞缪尔著关系数据库已经存在了30年，但他们不是原种的数据库，他们也不是最新的数据库。
2021大数据知识竞赛考试题及答案
2021大数据知识竞赛考试题及答案1、以下哪项不属于大数据的特征？数据量大数据类型复杂单位处理数据的速度高数据价值密度高【正确答案】2、以下哪项不属于大数据流式处理典型业务应用场景？实时营销实时服务实时监控用户画像【正确答案】3、以下不属于Hadoop内核的组成部分的是HDFSMapReduceHbase【正确答案】YARN4、HDFS默认的当前工作目录是/user/$USER，的值需要在下列哪一个配置文件内说明？mapred-site.xmlcore-site.xml【正确答案】hdfs-site.xml以上均不是5、下列哪一项不属于HDFS相对于分布式系统而言特有的特性？高容错大文件存储大量的随机读应用【正确答案】高吞吐量6、下列存储HDFS某一时段NameNode内存元数据信息的是hdfs-site.xmlfsimage【正确答案】editsfstime7、以下哪个不是HDFS的守护进程？secondarynamenodedatanodemrappmaster/yarnchild【正确答案】namenode8、关于 SecondaryNameNode 哪项是正确的？它是 NameNode 的热备它是内存没有要求它的目的是帮助 NameNode 合并编辑日志，减少 NameNode 启动时间【正确答案】SecondaryNameNode 应与 NameNode 部署到一个节点9、以下哪一项不属于HDFS集群中的namenode职责维护HDFS集群的目录树结构维护HDFS集群的所有数据块的分布、副本数和负载均衡负责保存客户端上传的数据【正确答案】响应客户端的所有读写数据请求10、以下哪一项属于SecondaryNamenode的作用监控Namenode管理Datanode合并fsimage和editlogs【正确答案】支持Namenode HA11、下面哪个程序负责 HDFS 中实际数据的存储NameNodeJobtrackerDatanode【正确答案】secondaryNameNode12、关于HDFS集群中的DataNode的描述不正确的是DataNode之间不是独立的，相互之间会有通信和数据传输存储客户端上传的数据的数据块一个DataNode上存储的所有数据块可以有相同的【正确答案】响应客户端的所有读写数据请求，为客户端的存储和读取数据提供支撑13、如果我们现有一个hadoop集群，默认存储文件3份，并且大文件会按照128M 的数据块大小进行切割分散存储，在不修改默认配置的情况下存储200个每个200M的文本文件，请问最终会在集群中产生多少个数据块（包括副本）？200400004001200【正确答案】14、下列选项中，哪一项是存储HDFS某一时段NameNode内存元数据信息？hdfs-site.xmlfsimage【正确答案】editsfstime15、HBase底层依靠什么进行数据的存储HDFS【正确答案】HiveMemoryMapReduce16、下列选项中，哪个选项是用于处理海量数据的并行编程模式和大规模数据集的并行运算的软件架构？GFSMapReduce【正确答案】ChubbyBitTable17、Mapreduce擅长哪个领域的计算离线批处理【正确答案】DAG计算流式计算实时计算18、在MapReduce中哪一个阶段，把Mapper的输出数据归并整理后分发给Reducer处理Shuffle【正确答案】MapReduceSort19、关于MapReduce原理，下面说法错误的是分为Map和Reduce两个阶段Map阶段由一系列Map任务组成Reduce阶段由一系列Reduce任务组成Map阶段与Reduce阶段没有任何依赖关系【正确答案】20、下列哪个程序通常与NameNode 在同一个节点启动TaskTrackerDataNodeSecondaryNameNodeJobtracker【正确答案】21、MapReduce的Map函数产生很多的keyvalue<key,value>【正确答案】Hash22、下面关于Hive，说法错误的是Hive支持所有标准SQL语法【正确答案】Hive底层采用的计算引擎是MapReduceHive提供的HQL语法，与传统SQL很类似Hive Server可采用MySQL存储元数据信息23、下列哪项通常是Hadoop中MapReduce集群的最主要瓶颈CPU网络磁盘【正确答案】内存24、Hadoop框架的缺陷不包括MR编程框架的限制过多的磁盘操作,缺乏对分布式内存的支持无法高效低支持迭代式计算海量的数据存储【正确答案】25、YARN的调度算法不包括以下哪种FIFO SchedulerFair SchedulerCapacity SchedulerStack Scheduler【正确答案】26、YARN和MapReduce的关系是MapReduce是一个计算框架，可运行在YARN之上【正确答案】YARN是一个计算框架，可运行在MapReduce之上MapReduce和YARN无直接关系以上回答均不正确27、下列选项中，哪个是用来将Hadoop和关系型数据库中的数据相互转移的工具？ZookeeperSqoop【正确答案】HIVESpark28、Hadoop 大数据平台在整个数据挖掘的过程中，起到的作用是数据源处理数据清洗和装载【正确答案】数据展现CUBE生成29、以下哪一项是大数据的核心告知与许可预测【正确答案】匿名化规模化30、以下哪一项是用于处理海量数据的并行编程模式和大规模数据集的并行运算的软件架构。
银行计算机岗位笔试题库及答案
银行计算机岗位笔试题库及答案一、选择题1. 下面哪个不是计算机的基本组成部分？A. CPUB. 显卡C. 内存D. 硬盘答案：B2. 以下哪个不是计算机网络的分类？A. 局域网B. 广域网C. 互联网D. 电子邮件答案：D3. 下面哪个不是相关性数据库的特点？A. 数据存储在多个表中B. 数据之间存在关联关系C. 提供方便的数据查询功能D. 主要用于高并发读写操作答案：D4. 以下哪个不是计算机网络中常用的传输介质？A. 光纤B. 电缆C. 热空气D. 无线信号答案：C5. 下面哪种密码学方法是非对称加密算法？A. DESB. AESC. RSAD. MD5答案：C二、填空题1. OSI模型共分为__7__层。
答案：72. 常用的面向对象编程语言有__Java__、__C++__。
答案：Java、C++3. SQL是结构化查询语言的缩写，全称为__Structured Query Language__。
答案：Structured Query Language4. HTML是超文本标记语言的缩写，全称为__HyperText Markup Language__。
答案：HyperText Markup Language5. CPU的全称是__Central Processing Unit__。
答案：Central Processing Unit三、简答题1. 什么是冯·诺伊曼体系结构？它的特点是什么？答：冯·诺伊曼体系结构是一种计算机体系结构，其主要特点是程序和数据存储在同一块内存中。
它具有存储程序控制、按指令序列执行、以二进制形式表示指令和数据等特点。
2. 请简述计算机网络的作用和优势。
答：计算机网络的作用是实现多台计算机之间的通信和资源共享。
它可以提供高效的数据传输、便捷的信息交流和共享、扩展计算资源以及提高工作效率等优势。
3. 请简述关系型数据库和非关系型数据库之间的区别。
程序员知识考试题库 通用版【有答案】
程序员知识考试题库通用版【有答案】1. 数据类型1.1 以下哪个不是 JavaScript 中的数据类型？- a) Number- b) String- c) Boolean- d) Object答案: d1.2 在 Python 中，以下哪个是基本数据类型？- a) List- b) Dictionary- c) Tuple- d) Set答案: c2. 数据结构2.1 以下哪个数据结构不是线性结构？- a) Stack- b) Queue- c) Tree- d) Graph答案: d2.2 在 Java 中，以下哪个集合类实现了栈的功能？- a) HashSet- b) ArrayList- c) LinkedList- d) Stack答案: d3. 网络协议- a) 80- b) 443- c) 8080- d) 22答案: a3.2 TCP 协议是基于什么传输数据的？- a) 电信号- b) 光信号- c) 数字信号- d) 声音信号答案: c4. 数据库4.1 SQL 是什么的缩写？- a) Simple Query Language- b) Structured Query Language- c) Server Query Language- d) System Query Language答案: b4.2 在 SQL 中，以下哪条语句可以用来删除表中的所有记录？- a) TRUNCATE TABLE- b) DELETE FROM- c) DROP TABLE- d) REMOVE FROM答案: a5. 编程语言5.1 JavaScript 中，以下哪个变量声明关键字用于定义对象？- a) var- b) const- c) let- d) function答案: c5.2 Python 中，以下哪个循环语句用于遍历集合类型的数据？- a) for- b) while- c) do-while- d) foreach答案: a以上是程序员知识考试题库的一部分，希望对您有所帮助！如有任何问题，请随时与我联系。
数据库英文版第六版课后答案
数据库英文版第六版课后答案Chapter 1: IntroductionQuestions1.What is a database?A database is a collection of organized and structured data stored electronically in a computer system. It allows users to efficiently store, retrieve, and manipulate large amounts of data.2.What are the advantages of using a database system?–Data sharing and integration: A database system allows multiple users to access and share data simultaneously.–Data consistency and integrity: A database system enforces rules and constraints to maintain the accuracy and integrity of the data.–Data security: A database system provides access control mechanisms to ensure that data is accessed by authorized users only.–Data independence: A database system separates the data from the application programs that use it, allowing for easier applicationdevelopment and maintenance.Exercises1.Discuss the advantages and disadvantages of using a database system.Advantages:–Data sharing and integration–Data consistency and integrity–Data security–Data independenceDisadvantages:–Cost: Database systems can be expensive to set up and maintain.–Complexity: Database systems require a certain level of expertise to design, implement, and manage.–Performance overhead: Database systems may introduce some overhead in terms of storage and processing.Overall, the advantages of using a database system outweigh the disadvantages in most cases, especially for large-scale applications with multiple users and complex data requirements.Chapter 2: Relational Model and Relational Algebra Questions1.What is a relation? How is it represented in the relational model?A relation is a table-like structure that represents a set of related data. It is represented as a two-dimensional table with rows and columns, where each row corresponds to a record and each column corresponds to a attribute or field.2.What is the primary key of a relation?The primary key of a relation is a unique identifier for each record in the relation. It is used to ensure the uniqueness and integrity of the data.Exercises1.Consider the following relation:Employees (EmpID, Name, Age, Salary)–EmpID is the primary key of the Employees relation.–Name, Age, and Salary are attributes of the Employees relation.2.Write a relational algebra expression to retrieve the names of all employees whose age is greater than 30.π Name (σ Age > 30 (Employees))Chapter 3: SQLQuestions1.What is SQL?SQL (Structured Query Language) is a programming language designed for managing and manipulating relational databases. It provides a set of commands and statements that allow users to create, modify, and query databases.2.What are the main components of an SQL statement?An SQL statement consists of the following main components:–Keywords: SQL commands and instructions.–Clauses: Criteria and conditions that specify what data to retrieve or modify.–Expressions: Values, variables, or calculations used in SQL statements.–Operators: Symbols used to perform operations on data. Exercises1.Write an SQL statement to create a table called。
cypher语句
cypher语句Cypher语句Cypher语句是一种基于图形数据库的SQL查询语言，它可以用来查询图形数据库中的数据。
它被称为图形查询语言（Graph Query Language），它有助于管理和查询图形数据库中构成节点和关系的数据。
Cypher语句有助于广大用户索引、抽取和操作数据，通过查询图形数据库来得到有价值的信息。
Cypher语句的简介Cypher语句是一种图形数据库查询语言，它可以帮助用户查询图形数据库中的数据。
它使用节点和关系来描述数据，对于查询非常有效。
它由关键字（如MATCH、RETURN、WHERE等）和函数（如UNION、COLLECT等）组成，可以构成复杂的查询。
Cypher语句的特点Cypher语句的优点包括：（1）Cypher语句的语法清晰，容易阅读；（2）它可以使用可读性强的方式来表达复杂的查询，从而提高效率；（3）它可以使用多种形式（如JSON、XML等）来表示结果；（4）它可以让用户利用不同的查询方式，自由搜索图形数据库中的数据，拓展查询能力；（5）它支持无论是增加新数据，还是修改、删除已有数据，都可以使用Cypher语句来实现。
Cypher语句的应用Cypher语句是一种多功能的SQL查询语言，可以提供给用户多种查询方式。
Cypher语句通常用于处理大规模图形数据库中存储的数据，可以更好地为用户提供查询服务。
它可以帮助用户从图形数据库中检索、抽取、分析以及处理出有价值的信息，为用户提供一套完整的查询系统。
此外，Cypher语句还可用于构建复杂的数据应用程序，它可以很好地集成到数据应用程序中，帮助开发者更好地实现业务的需求。
结论Cypher语句是一种用于图形数据库的SQL查询语言，使用其可以使用节点和关系查询图形数据库中的数据，进而得到有价值的信息。
它具有语法清晰、可读性强等优点，常用于处理图形数据库中存储的大规模数据，也可以用于构建复杂的数据应用程序。
neo4j cql shortestpath 用法
一、介绍Neo4j是一个高性能的图数据库，它使用Cypher查询语言（CQL）来操作图数据。
其中，shortestpath是Cypher查询语言中用于查找图中两个节点之间最短路径的功能。
本文将介绍如何使用neo4j的CQL语言来实现shortestpath功能以及常见的用法和注意事项。
二、最短路径概念在图数据库中，最短路径指的是在图中找到两个节点之间的最短路径，即经过的边的权重之和最小。
这个问题可以被抽象为图论中的最短路径算法，比如Dijkstra算法和Floyd-Warshall算法。
在neo4j中，我们可以使用CQL语言来实现最短路径的查找。
三、最短路径函数在neo4j中，通过使用MATCH和RETURN语句结合最短路径函数来查找最短路径。
最短路径函数的基本语法如下：MATCH (start:Node {name:"A"}) , (end:Node {name:"B"})CALL algo.shortestPath.stream(start, end, "weight")YIELD nodeId, costRETURN algo.asNode(nodeId).name AS node, cost上述语句中，start和end分别表示起始节点和目标节点，"weight"表示边的权重字段。
函数将返回节点和路径的cost，即最短路径的权重和。
通过调用这个函数，我们可以实现最短路径的查找。
四、最短路径实例假设我们有一个图数据库，其中包含若干节点和带有权重的边。
我们希望找到节点A到节点B的最短路径。
我们可以使用如下CQL语句来实现：MATCH (start:Node {name:"A"}) , (end:Node {name:"B"})CALL algo.shortestPath.stream(start, end, "weight")YIELD nodeId, costRETURN algo.asNode(nodeId).name AS node, cost通过执行上述语句，我们可以得到节点A到节点B的最短路径和其权重之和。
neo4j 计算机科学术语
neo4j 计算机科学术语
1.节点（Nodes）：在图形数据库中，节点代表实体，例如人、物体、地点等。
2. 属性（Properties）：节点和关系可以有一个或多个属性，属性是键值对，可以用来描述节点或关系的特征。
3. 关系（Relationships）：节点之间的边缘表示实体之间的关系。
例如，一个人可能和另一个人有“是朋友”的关系。
4. 标签（Labels）：标签是节点的集合。
标签可以用来分类节点。
5. Cypher 查询语言（Cypher Query Language）：Cypher 是Neo4j 的查询语言，它类似 SQL。
它被用来查询、创建和修改图形数据库。
6. 索引（Index）：索引是用于加速查询的数据结构。
节点的属性可以被索引，以便更快地查询特定的节点。
7. 图形数据库（Graph Database）：图形数据库是一个基于图形结构的数据库。
它使用节点、属性和关系来描述实体和它们之间的关系。
8. 递归查询（Recursive Query）：递归查询是一种可以检索具有任意深度的关系的查询。
它遍历图形数据库，直到找到所需的节点或关系。
9. 事务（Transaction）：Neo4j 支持 ACID 事务。
事务是一组操作，这些操作被当作单个操作来执行。
10. 嵌套查询（Nested Query）：嵌套查询是一种在查询中嵌入
子查询的查询。
这些子查询可以返回单个值、一组值或者一个表。
nebulagraph例子
nebulagraph例子英文回答：Nebula Graph is an open-source, distributed graph database that is designed to handle large-scale graph data. It provides a flexible data model that allows users to represent complex relationships between entities and perform efficient graph queries. With its distributed architecture, Nebula Graph can scale horizontally to handle massive amounts of data and achieve high availability.One of the key features of Nebula Graph is its ability to support real-time graph queries. This means that users can perform complex graph traversals and analytics on live data, enabling them to gain valuable insights and make informed decisions in real-time. For example, a social media platform could use Nebula Graph to analyze the connections between users and recommend relevant content or connections.Another important aspect of Nebula Graph is its support for high-performance graph queries. It uses an optimized storage and indexing mechanism to ensure fast query execution, even on large-scale graphs. This allows users to quickly retrieve and analyze graph data, enabling them to extract meaningful patterns and relationships. For instance, a fraud detection system could use Nebula Graph to identify suspicious patterns in financial transactions and prevent fraudulent activities.Nebula Graph also provides a user-friendly query language called Nebula Query Language (NQL) that allows users to interact with the database using familiar SQL-like syntax. This makes it easy for developers and datascientists to work with graph data without the need for extensive graph database knowledge. Additionally, Nebula Graph supports various connectors and integrations with popular programming languages and frameworks, making iteasy to integrate with existing data pipelines and applications.中文回答：Nebula Graph是一个开源的分布式图数据库，旨在处理大规模的图数据。
graphqlqueryresolver和graphqlresolver的用法
graphqlqueryresolver和graphqlresolver的用法GraphQL是一种用于API查询和数据操纵的查询语言和运行时环境。
它允许客户端以声明式的方式请求特定的数据，并只返回请求的数据，而不是整个响应。
GraphQL查询解析器（GraphQLQueryResolver）和数据解析器（GraphQLResolver）是用于在GraphQL服务器中处理查询请求和解析数据的重要组件。
在本文中，我们将逐步介绍这两者的用法和功能，并展示如何使用它们构建一个功能强大的GraphQL服务器。
1. 什么是GraphQL查询解析器（GraphQLQueryResolver）？GraphQL查询解析器是一个在GraphQL服务器中用于处理查询请求的组件。
它负责解析客户端发送的查询，并决定如何处理查询以及如何返回数据。
查询解析器是构建GraphQL服务器时的必需组件之一。
要创建一个查询解析器，我们首先需要定义一个GraphQL类型，该类型代表我们要查询的数据的结构。
让我们以一个图书列表为例，并定义一个名为Book的GraphQL类型，它有一个id字段和一个title字段。
javapublic class Book {private String id;private String title;Getters and Setters}接下来，我们需要创建一个GraphQL查询解析器类，并使用GraphQL 注解来标识我们要解析的查询和返回的数据。
javaimport com.coxautodev.graphql.tools.GraphQLQueryResolver;public class BookQueryResolver implements GraphQLQueryResolver {public Book getBook(String id) {通过ID从数据库或其他数据源获取图书对象Book book = bookRepository.getBookById(id);return book;}其他查询方法...}在上面的示例中，我们使用了一个名为getBook的方法来处理查询请求。
大规模图数据库管理中的查询优化与性能提升
大规模图数据库管理中的查询优化与性能提升近年来，图数据库作为互联网时代高效存储和处理大规模图数据的一种重要技术，得到了广泛的关注和应用。
然而，由于图数据的复杂性和规模庞大，图数据库的查询优化和性能提升成为了亟待解决的问题。
在大规模图数据库管理中，如何提升查询效率、减少查询时间，成为了图数据库开发者和研究者们共同面临的挑战。
查询优化是图数据库管理中的一项核心任务。
图数据库中的查询通常涉及到对大规模的节点和边的搜索、遍历、过滤和连接操作。
为了提高查询效率，有几个关键的方面需要考虑。
首先，图数据库需要设计高效的查询语言和查询接口。
传统的SQL查询语言不太适合图数据库中复杂的图查询操作。
因此，一些专门设计的图查询语言，如Cypher和GQL（Graph Query Language），被提出并得到了广泛应用。
这些语言支持图模式匹配、图遍历和属性过滤等操作，能够更加灵活高效地表达图查询需求，并能根据不同的查询特点进行优化。
其次，对于大规模图数据库管理，索引的设计和利用是非常重要的。
索引可以加快查询的速度，提升图数据库的性能。
图数据库通常会使用图结构索引和属性索引相结合的方式进行数据索引，以支持不同类型的查询。
图结构索引可以加速图遍历和节点连接操作，而属性索引可以加速属性过滤和图模式匹配。
基于图结构索引和属性索引的查询优化技术，如基于预排序的遍历和基于属性过滤的查询下推，被广泛研究和应用。
此外，分布式计算和存储技术也被用于大规模图数据库管理中的查询优化和性能提升。
由于图数据的规模和复杂性，单机环境下的查询往往无法满足性能需求。
因此，分布式图计算和存储框架，如Pregel、Giraph和GraphX，应运而生。
这些框架利用分布式计算和存储资源，将图查询任务划分为多个子任务进行并行计算，能够显著提升查询的效率和性能。
除了查询优化，还有一些其他方法和技术可以用于大规模图数据库管理中的性能提升。
一种方法是通过数据预处理和数据压缩来降低查询时间。
graphqlquery用法
graphqlquery用法
GraphQL查询语法包括以下部分：
1、查询（Query）：用于从后端获取数据。
查询通常以查询变量作为参数，可以获取特定的数据。
2、变异（Mutation）：用于向后端发送指令，进行数据的更改。
变异通常也需要以查询变量作为参数，可以更新特定的数据。
举一个例子，假设我们有一个商品管理系统，需要查询商品的列表，那么可以使用以下GraphQL查询语句：
graphql
query getShops {
shops {
id,
name,
tags
}
}
这个查询语句会返回所有商品的信息，包括商品的id、name和tags。
如果需要查询特定id 的商品，可以添加查询变量：
graphql
query getShop($id: ID!) {
shop(id: $id) {
id,
name,
tags
}
}
在这个查询语句中，我们需要传递一个名为“id”的参数，其值是我们需要查询的商品的id。
这个查询语句会返回对应id的商品的信息。
pquery 注释
pquery 注释pquery 注释指的是在编程语言中，对代码进行解释和说明的文字内容。
注释通常用于帮助他人理解代码的功能和作用，并且不会对程序运行结果产生任何影响。
注释可以在代码中任意位置插入，但是不会被编译器或解释器执行。
注释可以用中文或英文编写，一般以符号或关键词开头来标识。
在绝大多数编程语言中，常用的注释方式有两种：1. 单行注释：单行注释以特定符号或关键词开头，用于在代码的一行中添加注释。
在不同的编程语言中，符号和关键词可能有所不同。
例如，在Python中，使用井号(#)表示单行注释；在Java中，使用双斜杠(//)表示单行注释。
2. 多行注释：多行注释用于对代码块进行说明。
它可以跨越多行，并且通常以特定符号或关键词开始和结束。
在Python和JavaScript等语言中，使用三个单引号(''')或三个双引号(""")表示多行注释；在C++和Java等语言中，使用斜杠星号(/*)和星号斜杠(*/)表示多行注释。
下面是一个使用单行注释和多行注释的示例：```# 这是一个简单的示例程序# 首先定义了一个变量，并给它赋值为10number = 10# 接下来使用循环语句输出数字for i in range(number):print(i) # 打印当前数字'''这是一个多行注释的示例，用于说明上面的循环结构。
在循环内，会逐个打印数字。
'''```以上就是关于pquery 注释的中文解释，旨在帮助他人理解代码的功能和作用。
计算机技术与软件专业技术资格考试初级
一、选择题1.下列哪种编程语言主要用于网站后端开发？A.JavaScriptB.PHP（正确答案）C.CSSD.HTML2.在计算机存储中，1GB等于多少MB？A.1000MBB.1024MB（正确答案）C.512MBD.2048MB3.下列哪个软件是用于版本控制的？A.Microsoft WordB.Git（正确答案）C.Adobe PhotoshopD.Windows Media Player4.在数据库管理系统中，SQL代表什么？A.Structured Query Language（正确答案）B.Standard Query LanguageC.Simple Query LanguageD.Secure Query Language5.下列哪个是操作系统的一个例子？A.Microsoft ExcelB.Windows 10（正确答案）C.Google ChromeD.Adobe Illustrator6.哪种类型的软件测试是在代码编写完成后进行的，以检查代码的功能？A.单元测试（正确答案）B.集成测试C.系统测试D.验收测试7.在计算机网络中，HTTP代表什么？A.Hypertext Markup LanguageB.Hypertext Transfer Protocol（正确答案）C.Hypertext PreprocessorD.Hypertext Text Processor8.下列哪个不是编程语言的一种？A.PythonB.JavaC.C++D.PowerPoint（正确答案）。
Cypher用户指南说明书
Table of ContentsAbout1 Chapter 1: Getting started with cypher2 Remarks2 Versions2 Examples2 Keyword Guide2 Credits4AboutYou can share this PDF with anyone you feel could benefit from it, downloaded the latest version from: cypherIt is an unofficial and free cypher ebook created for educational purposes. All the content is extracted from Stack Overflow Documentation, which is written by many hardworking individuals at Stack Overflow. It is neither affiliated with Stack Overflow nor official cypher.The content is released under Creative Commons BY-SA, and the list of contributors to each chapter are provided in the credits section at the end of this book. Images may be copyright of their respective owners unless otherwise specified. All trademarks and registered trademarks are the property of their respective company owners.Use the content presented in this book at your own risk; it is not guaranteed to be correct nor accurate, please send your feedback and corrections to ********************Chapter 1: Getting started with cypherRemarksCypher is a declarative graph query language that allows for expressive and efficient querying and updating of a property graph.Cypher was originally created by Neo Technology for its graph database Neo4j, but was opened up through the openCypher project in October 2015 and has since been adopted by several other graph database vendors, including SAP HANA and AgensGraph.VersionsExamplesKeyword GuideRead KeywordsWrite KeywordsRead-Write KeywordsFilter KeywordsRemember to check the Refcard for your version of Cypher, as these may have changed.•current•3.23.1••3.0Read Getting started with cypher online: https:///cypher/topic/5399/getting-started-with-cypherCredits。
使用GraphQL构建API
使用GraphQL构建APIGraphQL是一种开放源代码数据查询和操作语言。
它是一种API查询语言和运行时环境，用于在客户端和服务器之间进行数据传输。
GraphQL允许客户端指定其需要的数据格式和数量，并在单个请求中获取所有所需的数据。
本文将介绍如何使用GraphQL构建API。
一、GraphQL概述GraphQL是Facebook于2012年开发的一种API查询语言和运行时环境，于2015年发布。
GraphQL旨在解决REST API存在的问题，例如，过度或不足的数据请求、多个查询引起的过度请求、固定数据结构和难以维护。
GraphQL具有以下特点：1.明确的查询：GraphQL可让客户端明确指定其所需的数据。
客户端可以指定查询的字段、变量、过滤器、分页等。
2.灵活的数据格式：GraphQL支持可选、嵌套和类型化的数据格式。
它可以很好地支持前端框架如React和Vue的组件模型。
3.精细的权限管理：GraphQL允许API开发人员定义各种级别的权限和保护机制，使得敏感数据仅可被授权的客户端或用户访问。
4.高效的网络请求：GraphQL允许客户端在单个请求中获取所需的所有数据。
5.可拓展的架构：GraphQL具有良好的拓展性能力，允许开发人员在不破坏现有API的情况下添加新功能。
二、GraphQL基础1.查询语法GraphQL有三种基本类型：查询、变量和字段。
一个完整的查询由这些部分构成，例如：```query ($page: Int!, $limit: Int!) {categories(page: $page, limit: $limit) {idnameposts {titlecontent}}}```上面的查询包括两个变量，分别是$page和$limit。
categories包含两个字段：id和name，posts是一个嵌套的字段，包含两个子字段：title和content。
在GraphQL中，查询字段可以是标量类型（字符串、数字等）或复杂类型（对象、列表等）。
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along the paths of a presentation graph based on the content information in the nodes (streams). We discuss e cient implementations of the new O-Algebra operators for the domain of multimedia presentation graphs. Observing that presentation graphs are probably sparse and not very large (possibly, graph with less than 50 nodes), we LeOz97, BBL 97] proposed a new schema based on Hu man Codes Hu 52], called the nodecode system, to represent presentation graphs. Using the nodecode system, we represent the path information for a presentation graph in compressed form, and we give di erent approaches, with and without nodecodes, to implement the algebra operators Next , Connected, and Until e ciently. The rest of the paper is organized as follows. In section 2, we present multimedia presentation graphs and the graph data model. In section 3, we present GOQL and illustrate it with examples in the context of multimedia presentation graphs. Section 4 discusses the query processing techniques for GOQL and elaborates the operators incorporated into O-Algebra for handling graphs. In sections 5 and 6, we discuss the nodecode system, and e cient implementations of the new algebra operators. In section 7, we give the related work. Section 8 concludes the paper.
Байду номын сангаас
Abstract
1 Introduction
Many database applications such as hypertext applications, geographic information systems, world wide web searching, and heterogeneous information integration, etc., require modeling and querying of graph data ( Guti94, GBPV 94, MeMM 96, BDHS 96, AQMWW 96, AM 98, FFKLS 98, LSBBOO98]). In this paper, we present a data model, and an OQL-like query language GOQL, for querying graphs. The data model is object-oriented and supports graphs. The query language GOQL is an extension of OQL Catt 96], enriched with constructs to create, manipulate and query objects of type graph, path and edge classes. GOQL can be used for any database application with a graph data model, or simply as a general query language whose data model is extended with graph, path, and edge classes. As in OQL, GOQL uses the traditional select...from...where statement for querying. GOQL extends OQL to express relationships between node objects, edge objects, path objects and graph objects as well as for construction, querying, and manipulation of such objects. Another feature of GOQL is its capability for querying sequences and paths (which are special cases of sequences). In addition to the sequence operators of OQL, GOQL uses the temporal operators next, until and connected for querying paths and sequences, so that queries involving relative ordering of sequence elements are supported. For processing, GOQL queries are translated into an operator-based language, O-Algebra LiOz96], extended with new operators. O-Algebra is an object algebra designed for processing object-oriented database (OODB) queries. O-Algebra o ers a small set of operators, and most of them are similar to their counterparts of the extended relational algebra. Operands of O-Algebra are sets of objects with a uniform structure - each object consists of an Oid and a tuple of at most one level of nesting. In processing, front-end objects are mapped to internal type objects. A general procedure is presented in LiOz96, LZO97] to convert OQL queries into O-Algebra expressions, which also reduces all nested queries during transformation. Since GOQL is an extension of OQL, to deal with path and sequence expressions, O-Algebra is extended with three temporal operators Next; Connected , and Until LSBHOO98], corresponding to the temporal operators Next; Connected, and Until, respectively. In this paper, we use multimedia presentation graphs as an application for GOQL. A multimedia presentation is a synchronized, and possibly interactive, delivery of multimedia data to users. The content of a multimedia presentation not only includes the contents of the individual multimedia streams in the presentation, but also speci es the playout order of these streams. In this paper, we assume that multimedia presentations are created and stored in the form of multimedia presentation graphs. We then use GOQL to select and store (parts of) multimedia presentation graphs with respect to their content, and to navigate 1