Postgres 9.6

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CREATE TABLE test (
    id int,
    name text,
    attr text
);

INSERT INTO test VALUES
(1, 'Bruce Wayne', 'is Batman'),
(2, 'Mickey Mouse', 'is not Batman'),
(3, 'Darkwing Duck', 'is close to Batman');

SELECT * FROM test;
3 rows affected



id
name
attr


1
Bruce Wayne
is Batman

2
Mickey Mouse
is not Batman

3
Darkwing Duck
is close to Batman


CREATE OR REPLACE FUNCTION my_function()
RETURNS int
AS $$
declare
  c int;
BEGIN
  CREATE TEMP TABLE saved_query AS
      SELECT * FROM test;
         
  c := (SELECT SUM(id) FROM saved_query);
  
  RETURN c;
END; $$

LANGUAGE plpgsql;
SELECT my_function();


my_function


6

id	name	attr
1	Bruce Wayne	is Batman
2	Mickey Mouse	is not Batman
3	Darkwing Duck	is close to Batman