Integrity Constraints
Integrity Constraints There are 1. domain integrity 2. entity integrity, 3. referential integrity 4. Enterprise integrity constraints. Domain Integrity Domain integrity means the definition of a valid set of values for an attribute. You define - data type, - lenght or size - is null value allowed - is the value unique or not for an attribute. You may also define the default value, the range (values in between) and/or specific values for the attribute. Some DBMS allow you to define the output format and/or input mask for the attribute. These definitions ensure that a specific attribute will have a right and proper value in the database. Entity Integrity Constraint The entity integrity constraint states that primary keys can't be null. There must be a proper value in the primary key field. This is because the primary key value is used to identify individual rows in a table. If there were null values for primary...