错误代码：1054。'where clause' 中的未知列 'sdate'

Question

我在查询中遇到了这个错误，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工作，但是当我将它合并到主查询时，sdate 变得未知。有什么想法吗？

我试图将 where 上的 sdate 替换为 at.startDate，但仍然得到未知的 at.startDate 列。

Answer 1

您不能在 where 子句中使用列别名。只用原来的列名：

where at.startDate between @startDate and @endDate

别名已被 order by 接受，因此无需更改。

Answer 2

我没有在主 select 子句中使用 selects，而是创建了一个子查询来加入，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

希望我在重构查询时没有搞砸任何事情 :)

错误代码：1054。'where clause' 中的未知列 'sdate'

Error Code: 1054. Unknown column 'sdate' in 'where clause'

mysql

sql

select

union-all