SQLSTATE 42702 ERROR Class 42: Syntax Error or Access Rule Violation

ambiguous_column Ambiguous Column — SQLSTATE 42702

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

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Last reviewed May 2025 Grounded in source

Symptoms

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.

Environment

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

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

Diagnostic Queries

Recovery

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).

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