Question

IN YOUR OWN WORD explain the primary, foreign, entity integrity rule, and referential integrity rule, and how they are important and relate to a structured database

Answer 1

The basis of Referential integrity is foreign keys.

A Foreign key in one table references a primary key in another table. The primary key for a table uniquely identifies entities (rows) in the table. Primary keys are maintained with entity integrity.

Entity integrity provides two properties for primary keys:

1. the primary key for a row is unique; it does not match the primary key of any other row in the table

2. the primary key is not null, no component of the primary key may be set to null

The uniqueness property rule ensures that the primary key for each row uniquely identifies and there are no duplicates. The second property ensures that there is meaning for everything

Referential integrity provides mechanism for foreign keys, it must specify that foreign key the table whose primary key is being referenced. It ensures only one property for foreign keys.