Foreign Key, on delete set null

Question

Am I misunderstanding something here? I have two tables, table1 and table2. Table2 has a foreign key that references a field in table1 with ON DELETE SET NULL associated with the foreign key. Table2 also has a TIMESTAMP field that has ON UPDATE CURRENT_TIMESTAMP set.

Modifying an entry in table2 successfully updates the timestamp field. Deleting the linked entry in table1 successfully sets the foreign key field in table2 to NULL, but does not update the TIMESTAMP field in table2.

When the field in in table2 gets set to NULL, isn't that considered an UPDATE, and the timestamp should get updated too?

Answer 1

This is documented, although not very clearly, in MySQL docs: InnoDB restrictions:

• Cascaded foreign key actions do not activate triggers.