> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# correlated_subqueries_* 会话设置

> ClickHouse 在 correlated_subqueries_* 自动生成分组中的会话设置。

export const SettingsInfoBlock = ({type, default_value, changeable_without_restart}) => {
  return <div className="not-prose" style={{
    display: "flex",
    flexWrap: "wrap",
    alignItems: "baseline",
    columnGap: "0.5rem",
    rowGap: "0.125rem",
    margin: "0.375rem 0",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <div style={{
    fontWeight: 600,
    opacity: 0.72
  }}>类型</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>默认值</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          无需重启即可更改
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

这些设置可在 [system.settings](/docs/zh/reference/system-tables/settings) 中查看，并由 [源代码](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp) 自动生成。

<div id="correlated_subqueries_default_join_kind">
  ## correlated\_subqueries\_default\_join\_kind
</div>

<SettingsInfoBlock type="DecorrelationJoinKind" default_value="right" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.11"},{"label": "right"},{"label": "新增设置。解关联查询计划的默认 JOIN 类型。"}]}, {"id": "row-2","items": [{"label": "25.10"},{"label": "right"},{"label": "新增设置。解关联查询计划的默认 JOIN 类型。"}]}]} />

控制解关联查询计划中的 JOIN 类型。默认值为 `right`，这意味着解关联后的查询计划将包含 RIGHT JOIN，且子查询输入位于右侧。

可能的值：

* `left` - 解关联过程将生成 LEFT JOIN，输入表将位于左侧。
* `right` - 解关联过程将生成 RIGHT JOIN，输入表将位于右侧。

<div id="correlated_subqueries_substitute_equivalent_expressions">
  ## correlated\_subqueries\_substitute\_equivalent\_expressions
</div>

<SettingsInfoBlock type="Bool" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.7"},{"label": "1"},{"label": "为关联子查询规划优化新增的设置。"}]}]} />

使用过滤表达式推断等效表达式，并用其替代创建 CROSS JOIN。

<div id="correlated_subqueries_use_in_memory_buffer">
  ## correlated\_subqueries\_use\_in\_memory\_buffer
</div>

<SettingsInfoBlock type="Bool" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.1"},{"label": "1"},{"label": "默认对关联子查询的输入使用内存中缓冲区。"}]}]} />

对关联子查询的输入使用内存中缓冲区，以避免重复求值。