---
type: concept
x-llmwiki:
  schemaVersion: "0.1"
  contentHash: 3170c2a662636763e60657ca8217a4264f1a03836cfede7c798db1fb1e2ed67d
  pageDirectory: concepts
  sources:
    - delta_duplicate_columns_found-error-condition-databricks-on-aws.md
  confidence: 1
  provenanceState: extracted
  freshnessStatus: unverified
  aliases:
    - delta-lake-partition-duplicate-detection
    - DLPDD
  citations:
    - file: delta_duplicate_columns_found-error-condition-databricks-on-aws.md
title: Delta Lake partition duplicate detection
description: Sub-conditions under DELTA_DUPLICATE_COLUMNS_FOUND that detect duplicate columns in partitioning contexts, including PARTITION_COLUMNS, PARTITION_SCHEMA, and CLUSTER_BY clauses.
tags:
  - delta-lake
  - partitioning
  - validation
timestamp: "2026-06-19T18:24:25.436Z"
---

# Delta Lake partition duplicate detection

**Delta Lake partition duplicate detection** refers to the error condition `DELTA_DUPLICATE_COLUMNS_FOUND` (SQLSTATE 42711) that occurs when Delta Lake identifies duplicate column names in operations involving partition columns or partition schemas. This error is part of a broader class of syntax errors (Class 42) and indicates that the system found duplicate column(s) at a point where uniqueness is required. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

## Partition‑related sub‑conditions

The `DELTA_DUPLICATE_COLUMNS_FOUND` error categorizes the location of the duplicate into several sub‑conditions. Two of these are directly relevant to partition handling:

| Sub‑condition | Description |
|---------------|-------------|
| `PARTITION_COLUMNS` | Duplicate column names were found in the partition columns specified for the operation. |
| `PARTITION_SCHEMA` | Duplicate column names were found in the partition schema of the table. |

^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

These sub‑conditions help identify whether the duplicate originated from the partition specification provided by the user (`PARTITION_COLUMNS`) or from the partition schema stored in the table metadata (`PARTITION_SCHEMA`).

## Other sub‑conditions

The error can also arise in contexts unrelated to partitions. The full list includes `ADDING_COLUMNS`, `CLUSTER_BY`, `CONVERT_TO_DELTA`, `DATA`, `EXISTING_SCHEMA`, `READ_SCHEMA`, `REPLACING_COLUMNS`, `SPECIFIED_COLUMNS`, and `TABLE_SCHEMA`. Each points to the specific stage where the duplicate was detected (e.g., while adding columns, during a `CLUSTER BY` clause, or in the data being saved). ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

## Impact on partitioning operations

When you define partition columns for a Delta table, each column name must be unique. Duplicate column names in the `PARTITIONED BY` clause or in the partition schema of an existing table will trigger this error. Similarly, operations such as `CONVERT TO DELTA` may fail if the source data contains duplicate column names in the partition specification. ^[delta_duplicate_columns_found-error-condition-databricks-on-aws.md]

## Related concepts

- [Delta Lake](/concepts/delta-lake.md) – The storage layer providing ACID transactions and partition pruning.
- Partition columns – Columns used to physically partition a Delta table for performance.
- Delta table schema – The logical schema including partition columns.
- [SQLSTATE 42711](/concepts/sqlstate-42711.md) – The SQL standard error code for duplicate column detection.
- Delta Lake error conditions – Other common error classes in Delta Lake on Databricks.

## Sources

- delta_duplicate_columns_found-error-condition-databricks-on-aws.md

# Citations

1. [delta_duplicate_columns_found-error-condition-databricks-on-aws.md](/references/delta_duplicate_columns_found-error-condition-databricks-on-aws-42950ac1.md)
