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42712 — Duplicate alias

PostgreSQL SQLSTATE 42712: Duplicate alias (duplicate_alias), source-backed diagnosis and recovery guidance.

42712 — Duplicate alias

At a glance

42712 is duplicate_alias: a query namespace assigns the same table alias more than once. The parser rejects two VALUES range-table entries named duplicate_alias.

Field Value
SQLSTATE 42712
Condition duplicate_alias
Status active
Known present by 7.4
Locked snapshots 9.0.23, 9.1.24, 9.2.24, 9.3.25, 9.4.26, 9.5.25, 9.6.24, 10.23, 11.22, 12.22, 13.23, 14.24, 15.19, 16.15, 17.11, 18.6, 19beta3
Macros ERRCODE_DUPLICATE_ALIAS
Aliases —

Meaning

Aliases are query names, so the second range-table entry is ambiguous before execution. This differs from a duplicate physical object (42710) and from repeated output column labels. Inspect every FROM/JOIN/CTE/subquery alias. The selected autocommit error leaves IDLE.

Diagnosis

Inspect every FROM, JOIN, CTE, and subquery alias, including aliases introduced by generated SQL. The duplicate is in the current query namespace, so search_path or renaming a base table is not the diagnosis.

Response

Give each range-table entry a distinct alias and qualify references. Renaming a base table or changing search_path does not repair the current query. In an explicit transaction, the failed parse leaves INERROR; roll back or return to a suitable savepoint before retrying. The selected autocommit path returns to IDLE.

Observed diagnostics

The fixed parser group is explicit ERROR with primary table name "%s" specified more than once and no detail or hint.

Representative case

The case uses two one-row VALUES relations with the same alias, then left_alias and right_alias, asserting both values.

SELECT * FROM (VALUES (1)) AS duplicate_alias(value), (VALUES (2)) AS duplicate_alias(value);
SELECT left_alias.value, right_alias.value FROM (VALUES (1)) AS left_alias(value), (VALUES (2)) AS right_alias(value);

The selected 18.6 and 10.21 runs passed SQLSTATE, severity, state/recovery, repair, cleanup, and isolated-target stop assertions. See case JSON and authored evidence; private manifest and registry hashes are recorded there.

Versions

The locked catalogue contains this condition from the 7.4 presence bound through the listed snapshots. The selected natural case passed on PostgreSQL 18.6 and 10.21; that bounded result does not infer every intermediate release or every source branch.

Sources

  • src.errcodes.REL_18_6 — fixed definition at 724edf9bde9d356724ad384a2e196edc3c9f80f7; SHA-256 6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba (source).
  • src.duplicate-alias.18.6 — src/backend/parser/parse_relation.c lines 471–474 at 724edf9bde9d356724ad384a2e196edc3c9f80f7; blob SHA-256 0d9c88f4a8def4c2d982c33f13208590e21ecf5e6f8cd9d7faa223dc771c9a9a (source).
  • src.duplicate-alias.10.23 — src/backend/parser/parse_relation.c lines 417–420 at 02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4; blob SHA-256 a34f40fc93fa5df0015fe5af5ee7761ccba2d16a791cda69ae07848ed27616b5 (source).
  • src.calls.REL_18_6 / src.calls.REL_10_23 — fixed call scans, SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf / 00d16d3eb01b71ccf1b245c8f3102f9d0ec9f36fb02777b8dd1b99fcb263040c.
  • manifest.42712 / snippet-registry.42712 — hashes are recorded in evidence/42712.json and each runtime record.