Specifying Domain CHECK Constraints
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You can specify a condition or requirement on a data value at the time the data is entered by applying a CHECK
constraint to a column. The CHECK
constraint in a domain definition sets a search condition (<dom_search_condition>) that must be true before data can be entered into columns based on the domain.
The syntax of the search condition is:
<dom_search_condition> = VALUE <operator> <val> | VALUE [NOT] BETWEEN <val> AND <val> | VALUE [NOT] LIKE <val> [ESCAPE <val>] | VALUE [NOT] IN (<val> [, <val> …]) | VALUE IS [NOT] NULL | VALUE [NOT] CONTAINING <val> | VALUE [NOT] STARTING [WITH] <val> | (<dom_search_condition>) | NOT <dom_search_condition> | <dom_search_condition> OR <dom_search_condition> | <dom_search_condition> AND <dom_search_condition> <operator> = {= | < | > | <= | >= | !< | !> | <> | !=}
The following restrictions apply to CHECK
constraints:
- A
CHECK
constraint cannot reference any other domain or column name. - A domain can have only one
CHECK
constraint. - You cannot override the domain’s
CHECK
constraint with a localCHECK
constraint. A column based on a domain can add additionalCHECK
constraints to the local column definition.