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sql: add note about table aliases in FOR UPDATE OF clause #21489

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3 changes: 2 additions & 1 deletion sql-statements/sql-statement-select.md
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Expand Up @@ -107,7 +107,8 @@ TableSample ::=

> **注意：**
>
> TiDB 从 v6.6.0 版本开始支持[使用资源管控 (Resource Control) 实现资源组限制和流控](/tidb-resource-control-ru-groups.md)功能。该功能可以将不同优先级的语句放在不同的资源组中执行，并为这些资源组分配不同的配额和优先级，可以达到更好的资源管控效果。在开启资源管控功能后，语句的调度主要受资源组的控制，`HIGH_PRIORITY` 将不再生效。建议在支持资源管控的版本优先使用资源管控功能。
> - TiDB 从 v8.5.6 版本开始支持在 `FOR UPDATE OF` 子句中使用表别名。为了兼容性，你仍然可以使用定义了别名的基础表名，但这会触发一个推荐使用显式别名的警告。当查询涉及多个具有相同名称但不同数据库的表时（例如 `FROM db1.t, db2.t FOR UPDATE OF t`），TiDB 现在会根据 `FROM` 子句中的顺序从左到右匹配目标表，而不是当前数据库的上下文。为避免歧义，建议在 `FOR UPDATE OF` 子句中指定数据库名称或使用别名。
> - TiDB 从 v6.6.0 版本开始支持[使用资源管控 (Resource Control) 实现资源组限制和流控](/tidb-resource-control-ru-groups.md)功能。该功能可以将不同优先级的语句放在不同的资源组中执行，并为这些资源组分配不同的配额和优先级，可以达到更好的资源管控效果。在开启资源管控功能后，语句的调度主要受资源组的控制，`HIGH_PRIORITY` 将不再生效。建议在支持资源管控的版本优先使用资源管控功能。

## 示例

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