> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-postgresql-tls-support.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# إعدادات الجلسة لـ use_variant_*

> إعدادات جلسة ClickHouse ضمن المجموعة المُولَّدة use_variant_*.

export const VersionHistory = ({rows = []}) => {
  if (rows.length === 0) {
    return null;
  }
  const headers = ["الإصدار", "القيمة الافتراضية", "ملاحظة"];
  const border = "1px solid rgba(128, 128, 128, 0.3)";
  const cell = {
    border,
    padding: "0.25rem 0.5rem",
    textAlign: "start",
    verticalAlign: "top"
  };
  return <details className="not-prose" style={{
    border,
    borderRadius: "0.5rem",
    margin: "0.5rem 0",
    padding: "0.5rem 0.75rem",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <summary style={{
    cursor: "pointer",
    fontWeight: 600,
    opacity: 0.72
  }}>
        سجل الإصدارات
      </summary>
      <table style={{
    borderCollapse: "collapse",
    width: "100%",
    margin: "0.5rem 0 0"
  }}>
        <thead>
          <tr>
            {headers.map(header => <th key={header} style={{
    ...cell,
    fontWeight: 600,
    opacity: 0.72
  }}>
                {header}
              </th>)}
          </tr>
        </thead>
        <tbody>
          {rows.map((row, row_index) => <tr key={row.id ?? row_index}>
              {(row.items ?? []).map((item, item_index) => <td key={item_index} style={{
    ...cell,
    overflowWrap: "anywhere"
  }}>
                  {item?.label}
                </td>)}
            </tr>)}
        </tbody>
      </table>
    </details>;
};

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
  }}>النوع</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>القيمة الافتراضية</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          يمكن تغييره دون إعادة التشغيل
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

هذه الإعدادات متاحة في [system.settings](/ar/reference/system-tables/settings)، وهي مُولَّدة تلقائيًا من [ملف المصدر](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

<div id="use_variant_as_common_type">
  ## use\_variant\_as\_common\_type
</div>

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

يسمح باستخدام النوع `Variant` كنوع ناتج لدوال [if](/ar/reference/functions/regular-functions/conditional-functions#if)/[multiIf](/ar/reference/functions/regular-functions/conditional-functions#multiIf)/[array](/ar/reference/functions/regular-functions/array-functions)/[map](/ar/reference/functions/regular-functions/tuple-map-functions) عندما لا يوجد نوع مشترك لأنواع المُعاملات.

مثال:

```sql theme={null}
SET use_variant_as_common_type = 1;
SELECT toTypeName(if(number % 2, number, range(number))) as variant_type FROM numbers(1);
SELECT if(number % 2, number, range(number)) as variant FROM numbers(5);
```

```text theme={null}
┌─variant_type───────────────────┐
│ Variant(Array(UInt64), UInt64) │
└────────────────────────────────┘
┌─variant───┐
│ []        │
│ 1         │
│ [0,1]     │
│ 3         │
│ [0,1,2,3] │
└───────────┘
```

```sql theme={null}
SET use_variant_as_common_type = 1;
SELECT toTypeName(multiIf((number % 4) = 0, 42, (number % 4) = 1, [1, 2, 3], (number % 4) = 2, 'Hello, World!', NULL)) AS variant_type FROM numbers(1);
SELECT multiIf((number % 4) = 0, 42, (number % 4) = 1, [1, 2, 3], (number % 4) = 2, 'Hello, World!', NULL) AS variant FROM numbers(4);
```

```text theme={null}
─variant_type─────────────────────────┐
│ Variant(Array(UInt8), String, UInt8) │
└──────────────────────────────────────┘

┌─variant───────┐
│ 42            │
│ [1,2,3]       │
│ Hello, World! │
│ ᴺᵁᴸᴸ          │
└───────────────┘
```

```sql theme={null}
SET use_variant_as_common_type = 1;
SELECT toTypeName(array(range(number), number, 'str_' || toString(number))) as array_of_variants_type from numbers(1);
SELECT array(range(number), number, 'str_' || toString(number)) as array_of_variants FROM numbers(3);
```

```text theme={null}
┌─array_of_variants_type────────────────────────┐
│ Array(Variant(Array(UInt64), String, UInt64)) │
└───────────────────────────────────────────────┘

┌─array_of_variants─┐
│ [[],0,'str_0']    │
│ [[0],1,'str_1']   │
│ [[0,1],2,'str_2'] │
└───────────────────┘
```

```sql theme={null}
SET use_variant_as_common_type = 1;
SELECT toTypeName(map('a', range(number), 'b', number, 'c', 'str_' || toString(number))) as map_of_variants_type from numbers(1);
SELECT map('a', range(number), 'b', number, 'c', 'str_' || toString(number)) as map_of_variants FROM numbers(3);
```

```text theme={null}
┌─map_of_variants_type────────────────────────────────┐
│ Map(String, Variant(Array(UInt64), String, UInt64)) │
└─────────────────────────────────────────────────────┘

┌─map_of_variants───────────────┐
│ {'a':[],'b':0,'c':'str_0'}    │
│ {'a':[0],'b':1,'c':'str_1'}   │
│ {'a':[0,1],'b':2,'c':'str_2'} │
└───────────────────────────────┘
```

<div id="use_variant_default_implementation_for_comparisons">
  ## use\_variant\_default\_implementation\_for\_comparisons
</div>

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

يُفعِّل أو يعطِّل التطبيق الافتراضي للنوع Variant في دوال المقارنة.