CHECK Conditions on Columns

You can apply a CHECK condition as a constraint on a table, instead of on a single column.

Such CHECK conditions typically specify that two values in a row being entered or modified have a proper relation to each other. Column CHECK conditions are held individually in the system tables, and can be replaced or deleted individually. CHECK conditions on individual columns are recommended where possible.

• Adding a Check Condition
  You can add a new CHECK condition to a table or to an individual column.
• Deleting a Check Condition
  You can delete a CHECK condition from an individual column.
• Replacing a Check Condition
  You can delete a CHECK condition from an individual column.