Database Systems

Question 1

Serial File

Answer 1

Serial File
- Data is stored in the order in which it is entered
- No order to data is maintained
- Useful for storing transactional and initialisation files

Question 2

Sequential Files

Answer 2

Sequential Files
- Stored in order of key fields
- Order is maintained when new records are added
- Useful for storing master files

Question 3

Flat File / Single table database

Answer 3

data is duplicated – this is not only inefficient use of storage it also means errors can occur between different records very easily which compromises integrity. This makes it harder to search the database (query a database)

Question 4

Flat vs Relational

Answer 4

Flat File Database
- single table
- Represented using
- Contains files, records, fields and characters
- simple to create, easy to use, inexpensive
- duplicated data therefore data inconsistences

Relational Database
- Consists of multiple entities
- Represented using entity relationship diagram
- Contains entity’s, attributes and relationships
- takes time to set up

Question 5

Primary and foreign keys

Answer 5

Primary key
- a unique identifier that uniquely identifies records.

Foreign key
- any field in table which is the primary key in another table

Question 6

Database management Systems (DBMS)

Answer 6

DBMS
- A manipulation language to change and access data
- Integrity to ensure efficiency and structure is not compromised
- Additional security
- Provides an interface for other programs to access data
- Program/data independence – You can change the data without affecting the program and vice versa.