ON DELETE SET NULL in postgres
ON DELETE SET NULL is a standard foreign key constraint option.
CREATE TABLE some_child ( parent_id integer references parent(id) on delete set null);or:
ALTER TABLE some_child ADD CONSTRAINT parent_id_fk FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE SET NULL;See the documentation.
In future posts make sure you include your PostgreSQL version and explain what you've already tried.