Database self-study Note 1

 

I. Important attributes of the database:
Persistent data refers to data stored in stable storage (such as disks ).
"Share"-meaning there are multiple methods for Databases
"Related"-connects data stored as independent units to provide a complete view
-Database-a collection of persistent data that can be shared and associated

2. Basic Features of commercial databases: persistent data, multiple users, multiple usage, and links to multiple entities

Three Database Management System DBMS-Database Management System
3.1: a collection of components that support data acquisition, distribution, maintenance, retrieval, and formatting.
3.2 DBMS public functions:
Database definition-language and graphical tools used to define entities, relationships, integrity constraints, and authorization
Non-process access-language and graphical tools that allow access to data without writing complex code
Application Development-graphical tools for development menus, data input forms, and reports.
Data in forms and reports must be specified in "non-process access" mode.
Programming Language Interface-combines non-process access with the complete functions of the Programming Language
Transaction Processing-a control mechanism used to prevent interference from concurrent users and recover lost data after a fault occurs
Database Optimization-this tool monitors and improves database performance

3.4. database definition:
When defining a database, you must specify the entity and associated relationship.
Entity-use tables to store entity sets
Join-Table connection
Table-two-dimensional data arrangement
SQL-Structured Query Language, used to define the relationship between tables, integrity constraints, and authorization between tables
Window graphics tools

3.5. Non-process access:
To use a language such as SQL, you only need to specify some parts of the database without writing complex program code. Does not include loop statements

3.6. application development and programming language interfaces
Combine non-procedural languages such as SQL with programming languages such as COBOL or Visual Basic.
For example, oracle PL/SQL

3.7. Support for database operations
Transaction Processing-used to handle a large number of repetitive tasks reliably and efficiently. DBMS ensures that concurrent users do not interfere with each other and faults do not cause work loss
Database Optimization-monitoring and utilities for improving performance

3.8. Third-party functions

4. Evolution of database technology

First generation-December 1960s-file structure and dedicated program interface-not DBMS
Second generation-1970s-network navigation-networks and layers of related records and standard program Interfaces
Third generation-1980s-relational-non-procedural language, optimization and transaction processing-IBM
Fourth generation-1990s-object multimedia, activity, distribution processing, more powerful operators, data warehouse processing, support for XML

5. Database Software
Oracle 9i 10g-Unix, Windows
IBM DB2, Informix-mvs as/400
Microsoft SQL Server-Windows
Other-Sybase, NCR terradata, Progress Software, MySQL, PostgreSQL, open source Ingres, and Firebird

Six DBMS Architecture
Data independence-A database should have its own identity for applications (programs, forms, and reports) that use it.
After separating identities, you can change the database definition without affecting related applications.
For example, if a new column is added to the table, applications that do not use this column will not be affected.
Three-mode architecture-A database description-based architecture is recommended to achieve data independence goals

View 1 View 2 view n external level externel-more-user level
|
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Conceptual mode concept level conceptual-greater-define entities and relationships (logical meaning)
|
Internal Mode internal level internal-more complex-represents the entire database (storage view)

Mode ing-describes how to derive a more advanced mode from a lower-level mode.
External-> concept level: ing can convert external view requests to table requests in conceptual mode.
Concept-> internal level: ing describes how to store objects to files
DBMS uses modes and ing to ensure data independence.

Distributed Processing-
Client/Server Architecture-clients, servers, and other components and data are distributed on computers connected through the network. This architecture allows clients and services

To effectively process messages (Service requests ).