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nontransactional dml FAQ about alias (#22523)#22536

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Mar 6, 2026
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nontransactional dml FAQ about alias (#22523)#22536
ti-chi-bot[bot] merged 2 commits intopingcap:release-7.1from
ti-chi-bot:cherry-pick-22523-to-release-7.1

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This is an automated cherry-pick of #22523

First-time contributors' checklist

What is changed, added or deleted? (Required)

Added FAQ about Unknown column error when using alias.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

  • master (the latest development version)
  • v9.0 (TiDB 9.0 versions)
  • v8.5 (TiDB 8.5 versions)
  • v8.1 (TiDB 8.1 versions)
  • v7.5 (TiDB 7.5 versions)
  • v7.1 (TiDB 7.1 versions)
  • v6.5 (TiDB 6.5 versions)
  • v6.1 (TiDB 6.1 versions)
  • v5.4 (TiDB 5.4 versions)

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Do your changes match any of the following descriptions?

  • Delete files
  • Change aliases
  • Need modification after applied to another branch
  • Might cause conflicts after applied to another branch

Oreoxmt and others added 2 commits March 6, 2026 02:57
@ti-chi-bot ti-chi-bot added lgtm needs-1-more-lgtm Indicates a PR needs 1 more LGTM. size/S Denotes a PR that changes 10-29 lines, ignoring generated files. type/cherry-pick-for-release-7.1 This PR is cherry-picked to release-7.1 from a source PR. labels Mar 6, 2026
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Summary of Changes

Hello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the TiDB documentation by addressing a common Unknown column error encountered when using table aliases in non-transactional DML statements. It provides a detailed explanation of the issue, its root cause (alias preservation during internal statement rewriting), and practical recommendations to prevent it, including avoiding aliases and utilizing DRY RUN for previewing statements. The changes aim to improve user experience by clarifying a tricky behavior and offering clear workarounds.

Highlights

  • New FAQ for 'Unknown column' error: A new FAQ section was added to the non-transactional-dml.md document, explaining the Unknown column '<alias>.<column>' in 'where clause' error that can occur when using table aliases in non-transactional DML statements.
  • Guidance on avoiding alias issues: The documentation now provides clear recommendations to avoid this error, including suggestions to avoid using table aliases directly and to utilize DRY RUN QUERY or DRY RUN to preview rewritten statements.
  • Warning in BATCH statement documentation: A prominent note was added to the sql-statements/sql-statement-batch.md file, alerting users to the potential alias-related error in BATCH statements and directing them to the more detailed FAQ for solutions.

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Changelog
  • non-transactional-dml.md
    • Added a new FAQ section titled 'The Unknown column '<alias>.<column>' in 'where clause' error occurs when using table aliases in non-transactional DML statements'.
    • Provided an explanation of why the error occurs due to internal statement rewriting not preserving aliases.
    • Included an example SQL statement that might trigger the error.
    • Listed recommendations to avoid the error, such as not using table aliases and using DRY RUN for preview.
  • sql-statements/sql-statement-batch.md
    • Inserted a note (> **Note:**) at the beginning of the document.
    • The note warns about the Unknown column error when using table aliases in BATCH statements.
    • It advises against using table aliases and suggests using DRY RUN QUERY or DRY RUN.
    • A link to the more detailed explanation in non-transactional-dml.md is provided.
Activity
  • This pull request is an automated cherry-pick of nontransactional dml FAQ about alias #22523.
  • The changes apply to master, v9.0, v8.5, v8.1, v7.5, and v7.1 branches.
  • The PR is translated from https://github.com/pingcap/docs-cn/pull/21313.
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Code Review

This pull request adds documentation regarding an Unknown column error that can occur when using table aliases in non-transactional DML statements. My review focuses on improving clarity and adhering to the documentation style guide. I've suggested minor changes to formatting and wording to enhance readability and avoid repetition.

Note: Security Review has been skipped due to the limited scope of the PR.


> **Note:**
>
> The `BATCH` statement is internally rewritten and split into multiple DML statements during execution. In the current version, table aliases might not be preserved, which can result in errors such as `Unknown column '<alias>.<column>' in 'where clause'`. To avoid this issue, do not use table aliases. Before execution, use `DRY RUN QUERY` or `DRY RUN` to preview the split statements before execution. For more information, see [Non-Transactional DML Statements](/non-transactional-dml.md).
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low

To improve clarity and avoid repetition, you can remove the redundant 'before execution' at the end of the sentence.

Suggested change
> The `BATCH` statement is internally rewritten and split into multiple DML statements during execution. In the current version, table aliases might not be preserved, which can result in errors such as `Unknown column '<alias>.<column>' in 'where clause'`. To avoid this issue, do not use table aliases. Before execution, use `DRY RUN QUERY` or `DRY RUN` to preview the split statements before execution. For more information, see [Non-Transactional DML Statements](/non-transactional-dml.md).
> The `BATCH` statement is internally rewritten and split into multiple DML statements during execution. In the current version, table aliases might not be preserved, which can result in errors such as `Unknown column '<alias>.<column>' in 'where clause'`. To avoid this issue, do not use table aliases. Before execution, use `DRY RUN QUERY` or `DRY RUN` to preview the split statements. For more information, see [Non-Transactional DML Statements](/non-transactional-dml.md).
References
  1. Avoid unnecessary words and repetition. (link)

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Oreoxmt commented Mar 6, 2026

/approve

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ti-chi-bot bot commented Mar 6, 2026

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Oreoxmt

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@ti-chi-bot ti-chi-bot bot added the approved label Mar 6, 2026
@ti-chi-bot ti-chi-bot bot merged commit 80db0da into pingcap:release-7.1 Mar 6, 2026
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@ti-chi-bot ti-chi-bot bot deleted the cherry-pick-22523-to-release-7.1 branch March 6, 2026 04:12
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