数据库系统课件 1-intro

8
File System
The first commercial database management systems appeared in the late 1960’s, Evolved from file system. Support
Store data over a long period of time. 1. Data cannot be lost if it is not backed up. 2. efficient access to data, whose location in a particular file is not known. 3. A query language for the data in files. 4. When concurrent access to file, one user don’t affect other users.
16
Evolution of DB Systems
17
Evolution of DB Systems
According to the data model, we say 1 generation:60’s
Hierarchical model Graph-based network model
2 generation:70’sRelation database system
Google searches. Queries at Amazon, eBay, etc.
7
People
DBMS implementor: builds system Database designer: establishes schema Database administrator: loads data, keeps whole thing running Database user: queries/modifies data
C.W.Bachman developed the IDS (IntegrБайду номын сангаасted Data Store)
one of the first database management systems
DBTG first report(1969) He is known to have had heated debates with Dr. E.F.Codd
14
Advantages of the Database Approach
Program-data independence Planned data redundancy Improved data consistency Improved data sharing Increased application development productivity Enforcement of standards Improved data quality Improved data accessibility and responsiveness Reduced program maintenance Improved decision support
User or an application program can access and modify data through a query language.
Transaction management
Supports concurrent access to data. Recover from failures or errors
4
Definitions
Database: organized collection of logically related data Data: stored representations of meaningful objects and events
Structured: numbers, text, dates Unstructured: images, video, documents
10
Problems with Data Redundancy
Waste of space to have duplicate data Causes more maintenance headaches The biggest problem:
Data changes in one file could cause inconsistencies Compromises in data integrity
5
Interesting Stuff About Databases
It used to be about : employee records, bank records, etc. Today, the field covers all the largest sources of data, with many new ideas.
Scientific and medical databases. Integrating information. Data mining.
6
Still More …
You may not notice it, but databases are behind almost everything you do on the Web.
12
Database Management System
A software system that is used to create, maintain, and provide controlled access to user databases
Order Filing System Central database Contains employee, order, inventory, pricing, and customer data
3
Objectives
Definition of terms Explain growth and importance of databases Name limitations of conventional file processing Explain advantages of databases Describe evolution of database systems List components of database implementation
ORACLE Microsoft SQL Server IBM DB2 SYBASE ,MY SQL……
23
DBMS’s major components
Query processor Storage and buffer manager Transaction processor
Logging and recovery Concurrency control
1973 ACM Turing Award
20
Relation Database System
1970 Proposed by E.F.Codd Data organized as tables Define relational data language
Relational algebra High-level Queries: SQL
11
SOLUTION: The DATABASE Approach
Central repository of shared data Data is managed by a controlling agent Stored in a standardized, convenient form
Requires a Database Management System (DBMS)
3 generation:80’sObject-Oriented database system…
18
Hierarchical model
Hierarchical model
IMS system(IBM,1968) dBASE,Foxbase/Foxpro,paradox…
19
Graph-based network model
Information: data processed to increase knowledge in the person using the data DBMS: a powerful tool for creating and managing data and allowing it to persist.
9
Not Support
Problems with Data Dependency
Each application programmer must maintain his/her own data Each application program must have its own processing routines for reading, inserting, updating, and deleting data Lack of coordination and central control Non-standard file formats
Invoicing System
DBMS
Payroll System
DBMS manages data resources like an operating system manages hardware resources
13
DBMS’s capabilities
Persistent storage Programming interface
2. Homeworks.
Individual.