Create Check Constraints

You can create a check constraint in a table to specify the data values that are acceptable in one or more columns in SQL Server 2012 by using SQL Server Management Studio or Transact-SQL.

In This Topic

• Before you begin:

  Security

• To create a new check constraint using:

  SQL Server Management Studio

  Transact-SQL

Before You Begin

Security

Permissions

Requires ALTER permissions on the table.

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Using SQL Server Management Studio

To create a new check constraint

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 (…).

3. In the Check Constraint Expression dialog box, type the SQL expressions for the check constraint. For example, to limit the entries in the SellEndDate column of the Product table to a value that is either greater than or equal to the date in the SellStartDate column or is a NULL value, type:

   SellEndDate >= SellStartDate OR SellEndDate IS NULL
   

   Or, to require entries in the zip column to be 5 digits, type:

   zip LIKE '[0-9][0-9][0-9][0-9][0-9]'
   

   Note

   Make sure to enclose any non-numeric constraint values in single quotation marks (').

4. Click OK.

5. In the Identity category, you can change the name of the check constraint and add a description (extended property) for the constraint.

6. In the Table Designer category, you can set when the constraint is enforced.

   To:	Select Yes in the Following Fields:
   Test the constraint on data that existed before you created the constraint	Check Existing Data On Creation Or Enabling
   Enforce the constraint whenever a replication operation occurs on this table	Enforce For Replication
   Enforce the constraint whenever a row of this table is inserted or updated	Enforce For INSERTs And UPDATEs

7. Click Close.

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Using Transact-SQL

To create a new check constraint

1. In Object Explorer, connect to an instance of Database Engine.

2. On the Standard bar, click New Query.

3. Copy and paste the following example into the query window and click Execute.

   ALTER TABLE dbo.DocExc 
      ADD ColumnD int NULL 
      CONSTRAINT CHK_ColumnD_DocExc 
      CHECK (ColumnD > 10 AND ColumnD < 50);
   GO
   -- Adding values that will pass the check constraint
   INSERT INTO dbo.DocExc (ColumnD) VALUES (49);
   GO
   -- Adding values that will fail the check constraint
   INSERT INTO dbo.DocExc (ColumnD) VALUES (55);
   GO
   

For more information, see ALTER TABLE (Transact-SQL).

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