> ## 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.

# count_distinct_* セッション設定

> count_distinct_* の生成グループに含まれる ClickHouse のセッション設定。

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
  }}>型</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>デフォルト値</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          再起動せずに変更可能
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

これらの設定は [system.settings](/docs/ja/reference/system-tables/settings) で確認でき、[ソースコード](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp) から自動生成されています。

<div id="count_distinct_implementation">
  ## count\_distinct\_implementation
</div>

<SettingsInfoBlock type="String" default_value="uniqExact" />

[COUNT(DISTINCT ...)](/docs/ja/reference/functions/aggregate-functions/count) の実行に使用する `uniq*` 関数を指定します。

設定可能な値:

* [uniq](/docs/ja/reference/functions/aggregate-functions/uniq)
* [uniqCombined](/docs/ja/reference/functions/aggregate-functions/uniqCombined)
* [uniqCombined64](/docs/ja/reference/functions/aggregate-functions/uniqCombined64)
* [uniqHLL12](/docs/ja/reference/functions/aggregate-functions/uniqHLL12)
* [uniqExact](/docs/ja/reference/functions/aggregate-functions/uniqExact)

<div id="count_distinct_optimization">
  ## count\_distinct\_optimization
</div>

<SettingsInfoBlock type="Bool" default_value="0" />

count distinct を group by のサブクエリに書き換える