Files and Relational Databases

Files and Relational Databases

What is a file?

• contains groups of records used to provide information for operations, planning, management and decision making.

• can be used for storing data for an indefinite period of time, or they can be used to store data temporarily for a specific purpose.

FILE TYPES

• Master Files -- contain records for a group of entities. The attributes may be updated often, but the records themselves are relatively permanent. These files tend to have large records containing all the information about a data entity. Examples : patient records, customer records, a personnel file, and a parts inventory file.

• Table Files -- contains data used to calculate more data or performance measures.

Examples : tax table and table of postage rates.

• Transaction Files -- used to enter changes that update the master file and produce reports. Examples : order record, payment record, purchase record, etc.

• Record Files -- very useful because users can take files to other computer systems and output to specialty devices. Examples : Employee Record, Medical Record, Criminal Record, Pupil Record

DATABASES

• A database is intended to be shared by many users.

• There are three structures for storing database files:

❑ Hierarchical database structures

❑ Network database structures

❑ Relational database structures

Hierarchical database structures

A kind of database management system that links records together like a family tree such that each record type has only one owner.

For example, an organization might store information about an employee, such as name, employee number, department, salary. The organization