27.5.4 The View WITH CHECK OPTION Clause

The WITH CHECK OPTION clause can be given for an updatable view to prevent inserts to rows for which the WHERE clause in the select_statement is not true. It also prevents updates to rows for which the WHERE clause is true but the update would cause it to be not true (in other words, it prevents visible rows from being updated to nonvisible rows).

In a WITH CHECK OPTION clause for an updatable view, the LOCAL and CASCADED keywords determine the scope of check testing when the view is defined in terms of another view. When neither keyword is given, the default is CASCADED.

WITH CHECK OPTION testing is standard-compliant:

• With LOCAL, the view WHERE clause is checked, then checking recurses to underlying views and applies the same rules.

• With CASCADED, the view WHERE clause is checked, then checking recurses to underlying views, adds WITH CASCADED CHECK OPTION to them (for purposes of the check; their definitions remain unchanged), and applies the same rules.

• With no check option, the view WHERE clause is not checked, then checking recurses to underlying views, and applies the same rules.

Consider the definitions for the following table and set of views:

CREATE TABLE t1 (a INT);
CREATE VIEW v1 AS SELECT * FROM t1 WHERE a < 2
WITH CHECK OPTION;
CREATE VIEW v2 AS SELECT * FROM v1 WHERE a > 0
WITH LOCAL CHECK OPTION;
CREATE VIEW v3 AS SELECT * FROM v1 WHERE a > 0
WITH CASCADED CHECK OPTION;

Here the v2 and v3 views are defined in terms of another view, v1.

Inserts for v2 are checked against its LOCAL check option, then the check recurses to v1 and the rules are applied again. The rules for v1 cause a check failure. The check for v3 also fails:

mysql> INSERT INTO v2 VALUES (2);
ERROR 1369 (HY000): CHECK OPTION failed 'test.v2'
mysql> INSERT INTO v3 VALUES (2);
ERROR 1369 (HY000): CHECK OPTION failed 'test.v3'