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sql-statement-explain: add explanation related to scalar subquery #19019

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sql-statement-explain: add explanation related to scalar subquery #19019

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@qiancai qiancai commented Sep 30, 2024

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@qiancai qiancai added area/planner Indicates that the Issue or PR belongs to the area of SQL planner or optimizer. translation/from-docs-cn This PR is translated from a PR in pingcap/docs-cn. labels Sep 30, 2024
@ti-chi-bot ti-chi-bot bot added the size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. label Sep 30, 2024
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hfxsd
hfxsd reviewed Sep 30, 2024
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sql-statements/sql-statement-explain.md
>
> Certain subqueries are pre-executed during the optimization phase to generate optimal execution plans, even in the `EXPLAIN` statement. For more information on this behavior and how to disable it, see [`tidb_opt_enable_non_eval_scalar_subquery`](/system-variables.md#tidb_opt_enable_non_eval_scalar_subquery-new-in-v730) and [Disable the early execution of subqueries](/explain-walkthrough.md#disable-the-early-execution-of-subqueries).

The statements `DESC` and `DESCRIBE` are aliases of the `EXPLAIN` statement. The alternative usage of `EXPLAIN <tableName>` is documented under [`SHOW [FULL] COLUMNS FROM`](/sql-statements/sql-statement-show-columns-from.md).
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Suggested change
The statements `DESC` and `DESCRIBE` are aliases of the `EXPLAIN` statement. The alternative usage of `EXPLAIN <tableName>` is documented under [`SHOW [FULL] COLUMNS FROM`](/sql-statements/sql-statement-show-columns-from.md).
The statements `DESC` and `DESCRIBE` are aliases of the `EXPLAIN` statement. The alternative usage of `EXPLAIN <tableName>` is documented in [`SHOW [FULL] COLUMNS FROM`](/sql-statements/sql-statement-show-columns-from.md).

@ti-chi-bot ti-chi-bot bot added the needs-1-more-lgtm Indicates a PR needs 1 more LGTM. label Sep 30, 2024
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ti-chi-bot bot commented Sep 30, 2024

[LGTM Timeline notifier]

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  • 2024-09-30 10:59:12.457069581 +0000 UTC m=+266107.877282587: ☑️ agreed by hfxsd.

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