SQL Constraints

This page demonstrates the concept of SQL constraints. Constraints are rules enforced by a database system to maintain data integrity. They prevent invalid or inconsistent data from being stored. These rules protect data integrity across a database. They ensure that data adheres to defined standards.

Let's explore a few example constraints:

Basic Constraints

Primary Keys

Foreign Keys

Not Null Constraints

Unique Constraints

Default Constraints

Composite Constraints

This is a simple example of a SQL constraint. Further constraints exist for more complex scenarios, focusing on data validation and maintaining the data's accuracy. Database systems use these constraints to enforce rules on data structure and integrity.

To learn more about SQL constraints, please refer to the official Microsoft documentation: https://docs.microsoft.com/en-us/sql/sql-constraints/?view=sql-server-ver16