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Database Systems
DBMS: database management system
Topics on database systems:
- DB systems concepts
- realtional model
- SQL
- E-R model
- DB design(RDB design)
- storage and file structure
- indexing
- Query Processing & Optimization
- Transaction
- Concurrency Control
- Recovery
Database Systems & DB design
Drawbacks of using file systems to store data:
- Data redundancy and inconsistency
- Difficulty in accessing data
- Data isolation
- Integrity problems
- Atomicity of updates
- Concurrent access by multiple users
- Security problems
- Data Dependence Problem
View of Data
- View level: describes only part of the entire database. Views can also hide information for security purpose
- Logical leve: describe what data stored in database, and what relationship among the data
- Physical level: describe how data are actually stored
DB language
- DDL(Data definition language)
Data dictionary contains metadata: database schema、Integrity constrains、Authorization
- DML(Data manipulation language) 操控
DML also konown as query language
Two classes of languages: Procedural、Declarative
SQL is the most widely used query language
- DCL
Query Processing: Parsing and translation、Optimization、Evalation
Query Processing Procedure:
