2019-05-05 17:38:05 +00:00
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# UUID函数
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下面列出了所有UUID的相关函数
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## generateUUIDv4 {#uuid_function-generate}
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生成一个UUID（[版本4](https://tools.ietf.org/html/rfc4122#section-4.4)）。
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```sql
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generateUUIDv4()
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```
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**返回值**
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UUID类型的值。
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**使用示例**
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此示例演示如何在表中创建UUID类型的列，并对其写入数据。
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``` sql
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:) CREATE TABLE t_uuid (x UUID) ENGINE=TinyLog
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:) INSERT INTO t_uuid SELECT generateUUIDv4()
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:) SELECT * FROM t_uuid
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┌────────────────────────────────────x─┐
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│ f4bf890f-f9dc-4332-ad5c-0c18e73f28e9 │
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└──────────────────────────────────────┘
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```
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## toUUID (x)
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将String类型的值转换为UUID类型的值。
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```sql
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toUUID(String)
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```
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**返回值**
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UUID类型的值
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**使用示例**
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``` sql
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:) SELECT toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0') AS uuid
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┌─────────────────────────────────uuid─┐
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│ 61f0c404-5cb3-11e7-907b-a6006ad3dba0 │
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└──────────────────────────────────────┘
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```
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## UUIDStringToNum
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接受一个String类型的值，其中包含36个字符且格式为`xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`，将其转换为UUID的数值并以[FixedString(16)](../../data_types/fixedstring.md)将其返回。
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``` sql
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UUIDStringToNum(String)
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```
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**返回值**
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FixedString(16)
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**使用示例**
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``` sql
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:) SELECT
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'612f3c40-5d3b-217e-707b-6a546a3d7b29' AS uuid,
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UUIDStringToNum(uuid) AS bytes
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┌─uuid─────────────────────────────────┬─bytes────────────┐
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│ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │ a/<@];!~p{jTj={) │
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└──────────────────────────────────────┴──────────────────┘
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```
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## UUIDNumToString
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接受一个[FixedString(16)](../../data_types/fixedstring.md)类型的值，返回其对应的String表现形式。
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``` sql
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UUIDNumToString(FixedString(16))
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```
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**返回值**
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String.
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**使用示例**
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``` sql
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SELECT
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'a/<@];!~p{jTj={)' AS bytes,
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UUIDNumToString(toFixedString(bytes, 16)) AS uuid
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┌─bytes────────────┬─uuid─────────────────────────────────┐
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│ a/<@];!~p{jTj={) │ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │
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└──────────────────┴──────────────────────────────────────┘
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```
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## 另请参阅
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- [dictGetUUID](ext_dict_functions.md)
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2019-06-07 11:06:23 +00:00
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- [dictGetUUIDOrDefault](ext_dict_functions.md#ext_dict_functions_dictGetTOrDefault)
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2019-05-05 17:38:05 +00:00
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[来源文章](https://clickhouse.yandex/docs/en/query_language/functions/uuid_function/) <!--hide-->
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