Store and reuse value returned by INSERT ... RETURNING

Question

In PostgreSQL, it is possible to put RETURNING at the end of an INSERT statement to return, say, the row's primary key value when that value is automatically set by a SERIAL type.

Question:

How do I store this value in a variable that can be used to insert values into other tables? Note that I want to insert the generated id into multiple tables. A WITH clause is, as far as I understand, only useful for a single insert. I take it that this will probably have to be done in PHP.

This is really the result of bad design; without a natural key, it is difficult to grab a unique row unless you have a handle on the primary key;

Answer 1

... that can be used to insert values into other tables?

You can even do that in a single SQL statement using a data-modifying CTE:

WITH ins1 AS (
   INSERT INTO tbl1(txt)
   VALUES ('foo')
   RETURNING tbl1_id
   )
INSERT INTO tbl2(tbl1_id)
SELECT * FROM ins1

Requires PostgreSQL 9.1 or later.

db<>fiddle here (Postgres 13)
_{Old sqlfiddle (Postgres 9.6)}

Reply to question update

You can also insert into multiple tables in a single query:

WITH ins1 AS (
   INSERT INTO tbl1(txt)
   VALUES ('bar')
   RETURNING tbl1_id
   )
 , ins2 AS (
   INSERT INTO tbl2(tbl1_id)
   SELECT tbl1_id FROM ins1
   )
INSERT INTO tbl3(tbl1_id)
SELECT tbl1_id FROM ins1;