if语句

IF 语句

IF (value1,value2,value3) value1 为布尔表达式或bu布尔值 value2 当value1结果为true时返回的结果 value3 当value1结果为false时返回的结果

例1:

SELECT IF(2=1,'对','错')AS status; 结果为:对 SELECT IF(2!=1,'对','错')AS status; 结果为:错

例1测试结果:

mysql> SELECT IF(2=1,'对','错')AS status; +--------+ | status | +--------+ | 错 | +--------+ 1 row in set

mysql> SELECT IF(2!=1,'对','错')AS status; +--------+ | status | +--------+ | 对 | +--------+ 1 row in set

mysql>

例2:

SELECT IF(true,'对','错')AS status; 结果为: 对 SELECT IF(false,'对','错')AS status; 结果为: 错

例2测试结果:

mysql> SELECT IF(true,'对','错')AS status; +--------+ | status | +--------+ | 对 | +--------+ 1 row in set

mysql> SELECT IF(false,'对','错')AS status; +--------+ | status | +--------+ | 错 | +--------+ 1 row in set

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