Relations of a Foreign KEY....

[rowlin]

Hello members,
What do they mean to set the relations of a Foreign KEY in "CASCADE", "SET NULL", "NO ACTION", "RESTRICT", "--" ?
Thank you. -- This message may have been cut off and the rest will only be shown to members. To become a member, click here --

[domin]

I cut and pasted this.

* CASCADE: Delete or update the row from the parent table and automatically delete or update the matching rows in the child table. Both ON DELETE CASCADE and ON UPDATE CASCADE are supported. Between two tables, you should not define several ON UPDATE CASCADE clauses that act on the same column in the parent table or in the child table.
* SET NULL: Delete or update the row from the parent table and set the foreign key column or columns in the child table to NULL. This is valid only if the foreign key columns do not have the NOT NULL qualifier specified. Both ON DELETE SET NULL and ON UPDATE SET NULL clauses are supported.
* NO ACTION: In standard SQL, NO ACTION means no action in the sense that an attempt to delete or update a primary key value is not allowed to proceed if there is a related foreign key value in the referenced table. InnoDB rejects the delete or update operation for the parent table.
* RESTRICT: Rejects the dele -- This message may have been cut off and the rest will only be shown to members. To become a member, click here --