Database environment consists of 3 components
- Users of the database
- Database management systems (DBMS)
- Physical database
Advantages of using a database environment
- Reduce date redundancy
- Reduced costs for date entry and data storage
- Data integrity is maintained and improved
- Improved data and information security
- Application software independence
- Standardization of data structures, data access, system software and file format
- Improved data access
Disadvantages of using a database environment
- Start-up and operating costs
- Complex to design and use
- Time consuming to design
- Database or database management software failure
Database users
- End-users
- Application programmers
- Database administrator
- Data administrator
- Database management systems (DBMS)
End-users
Capture data in the database and extract information form the database using database management system software
Application programmers
Responsible for creating, maintaining, updating and managing the application and DBMS software
Database administrator
Responsible for managing and controlling the organisation’s databases
Database administrator functions
- Implement and maintain database management standards and conventions
- Ensure applications software complies to database management standards and conventions
- Define the database structures
- Design and create databases in line with database management standards and conventions.
- Implement, maintain and evaluate database access policies and security controls
- Monitor data and database security and access.
Data administrator
Also called database analyst. Responsible for managing and controlling the data in the organisation’s databases
Database management systems (DBMS)
Integrated set of software that provides a user-friendly interface to the users for all data interactions between the user and the physical database
DBMS functions
- design, create and maintain the database structure and the database
- control the organisation, storage and retrieval of data in the database
- capture, maintain and manipulate the data in the database
- share data between multiple users simultaneously
- execute queries and generate outputs
- control the movement of the data between authorised users and the database
- control and monitor access to the database
- analyse and monitor database performance
Three-level database architecture
- External level
- Conceptual level
- Internal level
External level
User view, is the individual end-user’s view if the data and the database
Conceptual level
Complete view of the entire database
Internal level
Physical view, is the low-level view of how the data is physically stored on a storage device
DBMS Key components
- Data dictionary
* Database languages
Database dictionary
centralized file containing detailed information about the database and the data contained in the database
Information a database dictionary contains
- What data is stored in the database
- For each data field in the database, information
- Names and descriptions of the database files
- Each database file a list of attributes, primary keys and foreign keys included
- Authorized user groups for the database files and/or data fields
Database language
Database users use different database languages to interact with the database.
Database languages
- Data definition language
- Data control language
- Data manipulation language
- Data query language
Data definition language (DDL)
Used to define a database and includes commands to:
- create, modify and delete the database and database objects
- define and describe the data structure of the database according to the database model used
- create the data dictionary
Data control language (DCL)
Controls the security and user access to the database objects and data in the database
Data manipulation language (DML)
Routine operation of the database to insert, delete, modify and maintain the data stored on the database
Data query language
Used to retrieve data from the database
