nontransactional dml FAQ about alias (#22523)#22538
nontransactional dml FAQ about alias (#22523)#22538ti-chi-bot[bot] merged 2 commits intopingcap:release-8.1from
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Summary of ChangesHello, 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 specific issue where table aliases in non-transactional DML statements can lead to Highlights
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Code Review
This pull request adds documentation explaining the Unknown column error that can occur when using table aliases in non-transactional DML statements. The changes include a new FAQ section and a note in the BATCH statement documentation. My review includes a couple of minor suggestions to improve clarity and conciseness, in line with the repository's style guide.
Note: Security Review has been skipped due to the limited scope of the PR.
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| ### The `Unknown column '<alias>.<column>' in 'where clause'` error occurs when using table aliases in non-transactional DML statements | ||
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| When you execute a non-transactional DML statement, TiDB internally constructs a query for dividing batches and then generates the actual split execution statements. You can use [`DRY RUN QUERY`](/non-transactional-dml.md#query-the-batch-dividing-statement) and [`DRY RUN`](/non-transactional-dml.md#query-the-statements-corresponding-to-the-first-and-the-last-batches) to view these two types of statements, respectively. |
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For better clarity and readability, you can rephrase this sentence to be more direct.
| When you execute a non-transactional DML statement, TiDB internally constructs a query for dividing batches and then generates the actual split execution statements. You can use [`DRY RUN QUERY`](/non-transactional-dml.md#query-the-batch-dividing-statement) and [`DRY RUN`](/non-transactional-dml.md#query-the-statements-corresponding-to-the-first-and-the-last-batches) to view these two types of statements, respectively. | |
| When you execute a non-transactional DML statement, TiDB internally constructs a query for batch division and then generates the actual split statements for execution. You can use [`DRY RUN QUERY`](/non-transactional-dml.md#query-the-batch-dividing-statement) and [`DRY RUN`](/non-transactional-dml.md#query-the-statements-corresponding-to-the-first-and-the-last-batches) to view these two types of statements, respectively. |
References
- The style guide requires documentation to be clear and simple. This change improves readability. (link)
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| > **Note:** | ||
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| > 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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The phrase 'before execution' is used twice in this sentence, which is redundant. Removing the second occurrence makes the sentence more concise.
| > 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
- The style guide advises avoiding unnecessary words and repetition. This change removes a redundant phrase. (link)
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/approve |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: Oreoxmt The full list of commands accepted by this bot can be found here. The pull request process is described here DetailsNeeds approval from an approver in each of these files:
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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 columnerror 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).
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