DELETE Rule (delete_rule)

<delete_rule>::=
  ON DELETE CASCADE
| ON DELETE RESTRICT
| ON DELETE DEFAULT
| ON DELETE SET NULL
         

Explanation

• No DELETE rule: Deleting a row in the referenced table will fail if matching rows exist.

• ON DELETE CASCADE: If a row in the referenced table is deleted, all of the matching rows are deleted.

• ON DELETE RESTRICT: Deleting a row in the referenced table fails if matching rows exist.

• ON DELETE SET DEFAULT: If a row in the referenced table is deleted, the associated DEFAULT value is assigned to each matching row of each referencing column. A DEFAULT specification must exist for each referencing column.

• ON DELETE SET NULL: If a row in the referenced table is deleted, a NULL value is assigned to each referencing_column of each matching row. None of these referencing columns may be a NOT NULL column.