# CAST 函数

__*CAST 函数*__

+ 语法:
  + `CAST(expression AS TYPE)`
+ CAST 函数将任何类型的值转换为具有指定类型的值。目标类型可以是以下类型之一: `BINARY, CHAR, DATE, DATETIME, TIME, DECIMAL, SIGNED, UNSIGNED`
+ 比如:
  + `SELECT CAST(' ' as binary), binary(' ');`

```
tidb> select cast(' ' as binary), binary(' ');
+------------------------------------------+--------------------------+
| cast(' ' as binary)                      | binary(' ')              |
+------------------------------------------+--------------------------+
| 0x20                                     | 0x20                     |
+------------------------------------------+--------------------------+
1 row in set (0.00 sec)
```

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- Cast 函数和操作符表
  -  `BINARY`: 将一个字符串转换成一个二进制字符串
  -  `CAST()`: 将一个值转换成一个确定类型
  -  `CONVERT()`: 将一个值转换成一个确定类型