# 42701 — duplicate_column

> PostgreSQL SQLSTATE 42701: duplicate_column, source-backed diagnosis and recovery guidance.
---

# 42701

## At a glance {#at-a-glance}

SQLSTATE `42701` is **duplicate_column** in Class `42`. `42701` is duplicate_column. The selected CREATE TABLE path lists `id` twice and reports `column "%s" specified more than once` before a repaired table with distinct columns is created.

<!-- BEGIN SQLSTATE FACTS: generated by scripts/generate.py; do not edit -->

| Field | Value |
| --- | --- |
| SQLSTATE | `42701` |
| Condition | `duplicate_column` |
| 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_COLUMN` |
| Aliases | `—` |

<!-- source facts: data/errcodes/42701.json -->
<!-- END SQLSTATE FACTS -->

## Meaning {#meaning}

`42701` is duplicate_column. While processing a table definition, PostgreSQL compares the local `ColumnDef` names before merging inherited attributes. Listing the same name twice in one definition therefore reports `ERROR` `column "%s" specified more than once` before any repaired table is created. This local-name check is separate from inherited default, type, or collation conflicts, which can use other SQLSTATEs.

## Diagnosis {#diagnosis}

Inspect the generated column list after expansion, including quoted identifiers and migration fragments that are concatenated into one `CREATE TABLE`. PostgreSQL compares the identifier spelling after normal name processing, so an accidental repeated unquoted name is still one column name. The selected DDL `ERROR` leaves the autocommit session `IDLE`; inside an explicit `BEGIN`, the same error leaves the transaction `INERROR` until `ROLLBACK` or a suitable savepoint rollback before retrying. Distinguish this local duplicate-name branch from 42611's inherited-default conflict and from type/collation errors while merging inherited columns.

## Response {#response}

Remove the repeated definition or give it an intentional distinct name, rerun the complete DDL, and inspect the resulting catalog. If the duplicate came from a migration that already ran, compare the existing table definition before choosing `ALTER TABLE` versus a new `CREATE TABLE`; do not assume a failed `CREATE TABLE` partially created the relation. The selected repair creates `id` and `payload` and confirms two columns.

## Messages {#messages}

The selected `tablecmds.c` branch emits an explicit `ERROR` with primary `column "%s" specified more than once`; `%s` is the repeated column name. This message is about duplicate local column definitions, while neighboring source branches can report different SQLSTATEs for inherited type/collation conflicts. A client exception without the server SQLSTATE and primary is not sufficient to claim `42701`.

## Representative case {#case}

<!-- BEGIN SQLSTATE SNIPPET: duplicate_column -->

The page uses the same statements as the runner registry. Generated names such as `syntax_schema` and `syntax_role` are replaced by disposable runner values when executed.

```sql
CREATE TABLE syntax_schema.duplicate_table (id integer, id text);
CREATE TABLE syntax_schema.repaired_table (id integer, payload text);
SELECT count(*) FROM information_schema.columns WHERE table_schema = 'syntax_schema_name' AND table_name = 'repaired_table_name';
```

<!-- END SQLSTATE SNIPPET -->

The selected 18.6 run reports the structured diagnostic and passes the repair assertions; the 10.21 run passes the same case-specific checks. The downloadable case and evidence projections are [`42701 case JSON`](../data/cases/42701.json) and [`authored evidence`](../data/evidence/42701.json). The runner manifest is `verify/cases/42701/cases.json`, and the page SQL is checked against its shared registry.

## Versions {#versions}

The selected natural runtime scope is PostgreSQL 18.6 and 10.21; it does not infer behavior for every intermediate release.

## Related {#related}

- [`42611` — invalid_column_definition](../42611/)
- [`42703` — undefined_column](../42703/)

## Sources {#sources}

- `src.errcodes.18.6` — fixed `errcodes.txt` definition at commit `724edf9bde9d356724ad384a2e196edc3c9f80f7`; SHA-256 `6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/utils/errcodes.txt)).
- `src.duplicate-column.18.6` — `src/backend/commands/tablecmds.c` at `REL_18_6` commit `724edf9bde9d356724ad384a2e196edc3c9f80f7`; fixed blob SHA-256 `422dc8e833df4940755973c757e338295822ba3e4c7266c40669f49f96eb15a9` ([source](https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/commands/tablecmds.c#L2636-L2639)).
- `src.duplicate-column.10.23` — `src/backend/commands/tablecmds.c` at `REL_10_23` commit `02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4`; fixed blob SHA-256 `6de441c88496c6cf57a836898388085ec08bf69afd70d07acdafd6089b9b5f8c` ([source](https://github.com/postgres/postgres/blob/02991e79f8f58bc208f05dcc8af0c62dbe0a6ea4/src/backend/commands/tablecmds.c#L1741-L1744)).
- `src.calls.REL_18_6` / `src.calls.REL_10_23` — fixed call scans, SHA-256 `9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf` / `00d16d3eb01b71ccf1b245c8f3102f9d0ec9f36fb02777b8dd1b99fcb263040c`.