Create a Check Constraint on a table

Select the required table by clicking on it
Choose Object→Add Constraint
The new constraint will be added to the table the Inspector will display information about it.
Click on the Type field in the Inspector and choose CHECK as the type from the popup menu
Click on the Constraint Expression field in the Inspector then enter the constraint expression.

Note:

The contents of the Constraint Expression field will be exported without modification by SQLEditor.