MySQL为派生的最大功能列添加条件

Question

我有以下sql在where条件下不起作用。

SELECT t.PROJID,sum(t.UNITS) AS totalunits, sum(t.COST) AS totalcost, project, max(t.DATE) as lastupdated, PROJCODE 
FROM `projectcosts` `t` 
left join projects on projects.PROJID = t.PROJID 
where lastupdated LIKE '%2014-06-11%' 
GROUP BY t.PROJID

Answer 1

您不应该在日期上使用like 。 正确的解决方案是简单地截断日期并进行比较。 但是，您需要使用数据中的字段：

SELECT t.PROJID, sum(t.UNITS) AS totalunits,
       sum(t.COST) AS totalcost, project, max(t.DATE) as lastupdated, PROJCODE 
FROM `projectcosts` `t` left join
     projects on projects.PROJID = t.PROJID 
where date(t.date) = date('2014-06-11')
GROUP BY t.PROJID;

或者，如果您在lastupdated上具有索引，则使用范围可以使用索引：

SELECT t.PROJID, sum(t.UNITS) AS totalunits,
       sum(t.COST) AS totalcost, project, max(t.DATE) as lastupdated, PROJCODE 
FROM `projectcosts` `t` left join
     projects on projects.PROJID = t.PROJID 
where t.date >= date('2014-06-11') and t.date < date('2014-06-12')
GROUP BY t.PROJID;

您可能真的想使用having ，这是通过使用列别名而不是基础列来建议的。 在这种情况下：

SELECT t.PROJID, sum(t.UNITS) AS totalunits,
       sum(t.COST) AS totalcost, project, max(t.DATE) as lastupdated, PROJCODE 
FROM `projectcosts` `t` left join
     projects on projects.PROJID = t.PROJID 
GROUP BY t.PROJID
HAVING date(lastupdated) = date('2014-06-11');

Answer 2

Like不能与日期字段一起使用。 如果您将类型更改为vachar，则可以