如何使用“COUNT”条件在 MySQL 中？

Question

我在此查询中遇到错误，

SELECT count(if(state=0)) FROM `nagios`.`nagios_hostchecks`
where `nagios_hostchecks`.`start_time` like '%2012-01-02%'
and `nagios_hostchecks`.`host_object_id`=60;

Answer 1

这个怎么样：

SELECT count(*) 
FROM `nagios`.`nagios_hostchecks` 
WHERE `nagios_hostchecks`.`start_time` like '%2012-01-02%' 
    AND 
`nagios_hostchecks`.`host_object_id`=60
    AND
`state` = 0;

Answer 2

只是快速猜测，无需检查 nagios 架构

SELECT count(*) FROM nagios.nagios_hostchecks
WHERE state=0 AND nagios_hostchecks.start_time like '%2012-01-02%' 
AND nagios_hostchecks.host_object_id=60;