A check constraint specifies the data values or formats that are acceptable in one or more columns in a table. For example, you can require the zip column of the authors table to allow only five-digit numeric entries.
Note Some databases have different functionality for check constraints. For more information about the differences between databases, see Database Server Considerations. Consult your database documentation for details about how your database works with check constraints.
You can define many check constraints for a table. You use the Tables property pages to create, modify, or delete each check constraint.
| To | See |
| Attach a check constraint to a table to specify the data values that are acceptable in one or more columns | Attaching a New Check Constraint to a Table or Column |
| Create a constraint expression to check data for a condition | Defining a Check Constraint Expression |
| Change the constraint expression or the options that enable or disable the constraint for specific conditions | Modifying a Check Constraint |
| Apply constraints either to new data only or to existing data as well | Checking Existing Data When Creating a Check Constraint |
| Disable a check constraint when data is added to, updated in, or deleted from a table | Disabling a Check Constraint with INSERT and UPDATE Statements |
| Disable a check constraint when your table is replicated in another database | Disabling a Check Constraint for Replication |
| Remove the limitations on data values in a column | Deleting a Check Constraint |