syntax_error query has no destination for result data — 42601

Symptoms

A PL/pgSQL function ran a query that returns rows but did not capture them (no INTO, PERFORM, or RETURN QUERY). PostgreSQL raises SQLSTATE 42601 (syntax_error).

• A SELECT in PL/pgSQL has nowhere to send its results.
• Common when a bare SELECT is used instead of PERFORM.
• The hint suggests using PERFORM instead.

What the server log shows

ERROR:  query has no destination for result data
HINT:  If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT:  PL/pgSQL function check_user() line 5 at SQL statement

Why PostgreSQL raises this — what the manual says

Section 41.5.2 Executing SQL Commands (PERFORM):

“One might expect that writing SELECT directly would accomplish this result, but at present the only accepted way to do it is PERFORM.”

In PL/pgSQL, a query returning rows must direct them somewhere — INTO a variable, RETURN QUERY, or be discarded via PERFORM. A plain SELECT has no destination, so PostgreSQL rejects it with 42601.

Common causes

• Writing SELECT …; instead of PERFORM …; to run for side effects.
• Forgetting INTO when capturing a single-row result.
• Forgetting RETURN QUERY in a set-returning function.

How to fix it

1. Use PERFORM expr; to evaluate and discard results.
2. Use SELECT … INTO var; to capture a single-row result.
3. Use RETURN QUERY SELECT …; to return rows from a set-returning function.

Related & next steps

• SQLSTATE 42601 — Syntax Error (full reference)
• Message: RAISE EXCEPTION (P0001)
• Glossary: PL/pgSQL

Reference: PostgreSQL 18 Section 43.5 “Basic Statements”.