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On delete
On delete
Use this box to specify what action is to take
place on the dependent table when a row of the parent
table is deleted. The available actions are:
- RESTRICT
- Specifies that an error occurs for the DELETE
operation on the parent table and no rows are deleted.
A delete rule of RESTRICT is enforced before
all other constraints.
- NO ACTION
- Specifies that an error occurs for the DELETE
operation on the parent table and no rows are
deleted. The difference between NO ACTION and RESTRICT is
that NO ACTION is enforced
after other referential constraints while
RESTRICT is enforced before other referential
constraints.
- CASCADE
- Specifies that the DELETE operation on the parent
is propagated to the dependents of the deleted row in
the parent table.
- SET NULL
- Specifies that each nullable column of the foreign
key of each dependent of the deleted row is set
to null. Do not specify this action unless some
column of the foreign key allows null values.