ON DELETE SET NULL in postgres

Question

HI I'm new to postgresql environment so been lost for a while. I want to keep my data when parent entity is deleted. I want to know how to make 'ON DELETE SET NULL' for postgresql database. Please give me a clue.

Answer 1

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.