Sunday, August 16, 2020

Check Constraint in SQL Server

 Check constraint is used to limit the value that you can put into one column or multiple columns. This will specify a logical expression which will be evaluated every time a row is inserted or corresponding column is modified. 

check constraints help us to enforce data integrity and, in some cases, lead to better execution plans. It is a good idea to use them as long as you can live with the overhead that they introduce during data modification. 

You can get information about check constraints from the sys.check_constraints catalog view .


It is always best practice to use the constraint name during the creation.

create table dbo.Accounts


AccountId int not null identity(1,1),

AccountType varchar(32) not null,

Age int,

constraint CHK_Accounts_AccountType

check (AccountType in ('Checking','Saving','Credit Card')),

constraint CHK_Accounts_Age

check (Age> 18)


insert into Accounts values


Drop the Check Constraint

To drop a check constraint use the following SQL script.

Alter table Accounts

drop constraint CHK_Accounts_Age;

Add the Check Constraint



Different types of SQL Server Constraints:

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