Database 01

Why Study Databases
- many computing applications deal with large amounts of information
- Database systems give a set of tools for stoingm searching and managing this information

What is a Database
-  a set of informatino held in a computer
- one or more large structured sets of persistent data, usually associated with software to update and query the data
- a collection of data arranged for ease and speed of search and retrieval

Examples of Databases
- web indexes - library catalogues
- Medical records - airline bookings
- Bank accounts - Student records
- Stock control - customer histories
- Product Catalogues - Contact list
- etc....

Database Systems
 -a database system is consist of:
- Data
- Software
- Hardware
- Users
 - database systems allow users to
- store
- update
- retrieve
- organize
- protect
  their data

Database Users
- End Users - use the database system to achieve some goals
- Application Developers - write software to allow end users to interface with the database system
- Database Administrators - designs and manages the database system
- Database systems programmer - writes the database software itself

Database Management Systems
- a database os a collection of information
- a database management system (DBMS) is the software that controls that information
- examples :
- Oracle - MySQL
- SQLite - MS SQL Server
- PpostgreSQL - DB2 (IBM)

What the DBMS Does
- provides users with
- Data Definition Language (DDL)
- Data Manipulatin Language (DML)
- Data Control Language (DCL)
- DBMS provides
- Persistence
- Concurrency
- Integrity
- Security
- Data Independence

File Based Systems
- Data is stored in files
- Each file has a specific format
-Programs that use these files depend on knowledge about that format

Problems :
- No standards
- Data duplication
- Data dependence
- No way to generate ad hoc queries
- No provision for security, recovery,  concurrency, etc.