# **IS NOT**

## **语法说明**

`IS NOT` 运算符用于测试数值是否为布尔值，若不是布尔值，则返回结果为 `true`。其中 `boolean_value` 可以为 `TRUE`、`FALSE` 或 `UNKNOWN`。

## **语法结构**

```text
> IS NOT boolean_value
```

## **示例**

```text
mysql> SELECT 1 IS NOT TRUE, 0 IS NOT FALSE, NULL IS NOT UNKNOWN;
+---------------+----------------+---------------------+
| 1 is not true | 0 is not false | null is not unknown |
+---------------+----------------+---------------------+
| false         | false          | false               |
+---------------+----------------+---------------------+
1 row in set (0.01 sec)
```