How Do You Write a Check Constraint in Sql

The syntax for creating a check constraint in an ALTER TABLE statement in SQL Server (Transact-SQL) is: ALTER TABLE table_name ADD CONSTRAINT constraint_name CHECK (column_name condition); table_name. The name of the table that you wish to modify by adding a check constraint.

What is a check constraint in SQL?

A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table. … It can refer to a single column, or multiple columns of the table. The result of the predicate can be either TRUE , FALSE , or UNKNOWN , depending on the presence of NULLs.

How do I add a check constraint to an existing column in SQL?

1. In Object Explorer, expand the table to which you want to add a check constraint, right-click Constraints and click New Constraint.
2. In the Check Constraints dialog box, click in the Expression field and then click the ellipses (…).