Ambiguous Column — SQLSTATE 42702

SQLSTATE 42702 condition ambiguous_column class 42 — Syntax Error or Access Rule Violation severity ERROR
Reproduced & verified on PostgreSQL 14.23, 15.18, 16.14, 17.10 and 18.4 — identical message on every version.
Last reviewed 29 May 2025 · Reproduced live with the SQL on this page.

! Symptoms Free

A column reference is ambiguous — it matches more than one table in the query.

  • The error is written to the server log and returned to the client carrying SQLSTATE 42702.
  • Any driver (libpq, JDBC, psycopg, npgsql, pgx) surfaces this code in its error object so you can branch on it programmatically.
  • PL/pgSQL can trap it by name: EXCEPTION WHEN ambiguous_column THEN.

1 Environment & reproduce Free

Severity: ERROR  |  PostgreSQL versions: 12, 13, 14, 15, 16, 17

Reproduce with the exact statement and read the full message in the server log (raise log_min_messages / set log_min_error_statement for more context).

? Root cause Free

Two joined tables expose a column with the same name and the reference is unqualified.

3 Recovery & verify Free

Steps to resolve 42702:

  1. Qualify the column with its table or alias (for example a.id).

Reference: PostgreSQL error codes — Class 42 (Syntax Error or Access Rule Violation).