PostgreSQL error code

PostgreSQL error P0003

P0003 is the SQLSTATE PostgreSQL reports for too many rows, in class P0, PL/pgSQL Error.

SQLSTATE	P0003
Condition name	too_many_rows
Class	P0 — PL/pgSQL Error

Reproduce it, then fix it

SELECT INTO STRICT requires exactly one row, and there are several Electronics products. Narrow the WHERE clause to a single row, or loop over them all. Run the broken query to see the error, then switch to the fixed one. Edit either freely; every run is rolled back.

DO $$
DECLARE
  p products;
BEGIN
  SELECT * INTO STRICT p FROM products WHERE category = 'Electronics';
END $$;

DO $$
DECLARE
  p products;
BEGIN
  SELECT * INTO STRICT p FROM products WHERE category = 'Electronics' AND id = 1;
END $$;

Source: PostgreSQL documentation, Appendix A