> ## 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.

# function_json_* session settings

> ClickHouse session settings in the function_json_* generated group.

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
  }}>Type</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>Default</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          Changeable without restart
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

These settings are available in [system.settings](/docs/reference/system-tables/settings) and are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

<h2 id="function_json_value_return_type_allow_complex">
  function\_json\_value\_return\_type\_allow\_complex
</h2>

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

Control whether allow to return complex type (such as: struct, array, map) for json\_value function.

```sql theme={null}
SELECT JSON_VALUE('{"hello":{"world":"!"}}', '$.hello') settings function_json_value_return_type_allow_complex=true

┌─JSON_VALUE('{"hello":{"world":"!"}}', '$.hello')─┐
│ {"world":"!"}                                    │
└──────────────────────────────────────────────────┘

1 row in set. Elapsed: 0.001 sec.
```

Possible values:

* true — Allow.
* false — Disallow.

<h2 id="function_json_value_return_type_allow_nullable">
  function\_json\_value\_return\_type\_allow\_nullable
</h2>

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

Control whether allow to return `NULL` when value is not exist for JSON\_VALUE function.

```sql theme={null}
SELECT JSON_VALUE('{"hello":"world"}', '$.b') settings function_json_value_return_type_allow_nullable=true;

┌─JSON_VALUE('{"hello":"world"}', '$.b')─┐
│ ᴺᵁᴸᴸ                                   │
└────────────────────────────────────────┘

1 row in set. Elapsed: 0.001 sec.
```

Possible values:

* true — Allow.
* false — Disallow.