SQLSTATE 42P04 ERROR Class 42: Syntax Error or Access Rule Violation

duplicate_database Duplicate Database — SQLSTATE 42P04

A database with that name already exists.

PG 12, 13, 14, 15, 16, 17, 18 Official docs
Last reviewed May 2025 Grounded in source

Symptoms

A database with that name already exists.

  • The error is written to the server log and returned to the client carrying SQLSTATE 42P04.
  • 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 duplicate_database 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

CREATE DATABASE targets an existing name.

Diagnostic Queries

Recovery

Steps to resolve 42P04:

  1. Use a different name, or drop the existing database if it is safe to do so.

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

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