mysql - 错误代码 : 1054. 'sdate' 中的未知列 'where clause'

Question

我在查询中遇到此错误，您知道如何将 sdate 放入 2 层子查询中吗？

select
at.startDate as sdate, at.dau as DAU,
(
select count(distinct d.uid) from
 (select ses.uid from dsession as ses where ses.startDate = sdate group by ses.uid
  union all
  select res.uid from rsession as res where res.startDate = sdate group by res.uid) as te
) as MAU, (SELECT DAU/MAU) as AVG
from
attendance as at 

如果我单独查询子查询，它会起作用，但是当我将其合并到主查询时，sdate 变得未知。有什么想法吗？

我尝试将 where 上的 sdate 替换为 at.startDate，但仍然得到未知的 at.startDate 列.

Answer 1

我没有在主 select 子句中进行选择，而是创建了一个子查询来连接，以便可以检查 startDate

SELECT at.startDate AS sdate, at.dau AS DAU, (DAU/MAU.cnt) as AVG
FROM attendance AS at
JOIN (SELECT startdate, count(distinct uid) as cnt
      FROM (SELECT uid, startdate FROM dsession
            UNION ALL
            SELECT uid, startdate FROM rsession) as ua
      GROUP BY startdate
     ) as MAU ON MAU.startdate = at.startdate

希望我在重组查询时没有搞砸任何事情:)