MySQL IS和IS NOT运算符有什么用？
在MySQL中， IS和 ISNOT运算符均用于根据布尔值测试值。
IS运算符的语法可以如下-
Val IS Boolean_val
这里 瓦尔是我们要反对布尔值测试值。
Boolean_val 是将对其进行测试的布尔值，它可以是TRUE，FALSE或UNKNOWN。
ISNOT 运算符的语法可以如下-
Val IS NOT Boolean_val
这里 瓦尔 是我们要反对布尔值测试值。
Boolean_val 是将针对其测试val的布尔值，它可以为TRUE，FALSE或UNKNOWN。
以下MySQL语句将演示以上内容-
mysql> Select 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN; +-----------+------------+-----------------+ | 1 IS TRUE | 0 IS FALSE | NULL IS UNKNOWN | +-----------+------------+-----------------+ | 1 | 1 | 1 | +-----------+------------+-----------------+ 1 row in set (0.00 sec) 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 | +---------------+----------------+---------------------+ | 0 | 0 | 0 | +---------------+----------------+---------------------+ 1 row in set (0.00 sec) mysql> Select 0 IS NOT TRUE, 1 IS NOT FALSE, NULL IS NOT UNKNOWN; +---------------+----------------+---------------------+ | 0 IS NOT TRUE | 1 IS NOT FALSE | NULL IS NOT UNKNOWN | +---------------+----------------+---------------------+ | 1 | 1 | 0 | +---------------+----------------+---------------------+ 1 row in set (0.00 sec)
热门推荐
10 对患者生日祝福语简短
11 结婚祝福语简短装备
12 周岁祝福语学生文案简短
13 订婚领证祝福语简短精辟
14 导师获奖祝福语大全简短
15 新婚购房祝福语简短精辟
16 牛年祝福语简短的爱人
17 送芒果的祝福语简短
18 送给学长毕业祝福语简短