That only allows the deferral of the foreign key constraint check to commit time. It does not permit the addition of a child without a parent. To have an "orphan" child the referent is NULL. eg: ``` create table parent(id integer primary key); create table child(id integer primary key, parent references parent(id)); insert into parent default values; insert into child values (2, 1); insert into child values (3, null); insert into child values (5, 2); -- Error: FOREIGN KEY constraint failed select * from parent; -- 1 select * from child; -- 2|1 -- 3| ``` or, for example: ``` create table parent(id integer primary key); create table child(id integer primary key, parent references parent(id) on delete set null); insert into parent default values; insert into child values (2,1); select * from parent; -- 1 select * from child; -- 2|1 delete from parent where id == 1; select * from child; -- 2| ```