Check Constraints

A Check Constraint enforces domain integrity by limiting the values that are accepted by a column.

Access     In diagram or Project Browser | Right-click on Table | Features & Properties | Operations > Constraint | Add New Constraint  (Ctrl+N)

Create a Constraint

Step

Action

See also

1

On the Constraint tab of the Columns and Constraints screen, a new constraint is automatically created and assigned the default constraint name and a Type of index.

Overtype the constraint name with a name that identifies the constraint as a check constraint, such as CHK_ColumnName. (The CHK_ prefix is optional.)

 

 

2

In the Type field, change the value from index to check.

 

 

3

In the Condition property, type in the entire check constraint clause; for example, coll < 1000.

If the condition is long, click on the expansion button ( ... ) at the end of the field and type the condition into the  Check Condition for constraint <table name> dialog.

 

 

4

If necessary (and if the DBMS you are using supports it), you can type a formatted comment on the Check Constraint in the field on the Notes tab.

 

 

5

Click on the Close button.

 

 

Delete a Check Constraint

If you do not want to keep a check constraint, either:

·Right-click on it in the list and select Delete constraint '<name>', or
·Click on the item and press Ctrl+D

 

The constraint is immediately deleted.

Learning Center topics

·(Alt+F1) | Enterprise Architect | Database Engineering | Physical Data Model | Check Constraint