March 21st, 2010
Data Integrity
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B. SQL Basics
Data integrity is the consistency of data. The row(s) that are used for the primary key must have a value. This is called “Entity Integrity.” The row(s) that maintain relationship consistency between tables (foreign keys) are for “Referential Integrity.” Referential integrity requires that every foreign key value in one table must have a matching primary key value in the corresponding table or have a null (not used) value.For example, you may not allow a person to be added to the payroll table until that person has been entered into the employee table first.
