Define data, entity, domain and referential integrity.

Data Integrity Data Integrity validates the data before getting stored in the columns of the table. SQL Server supports four type of data integrity: Entity Integrity Entity Integrity can be enforced through indexes, UNIQUE constraints and PRIMARY KEY constraints.

Domain Integrity

Domain integrity validates data for a column of the table.
It can be enforced using:

Foreign key constraints,
Check constraints,
Default definitions
NOT NULL.

Referential Integrity

FOREIGN KEY and CHECK constraints are used to enforce Referential Integrity.

User-Defined Integrity

It enables you to create business logic which is not possible to develop using system constraints. You can use stored procedure, trigger and functions to create user-defined integrity.