Question

我有两个SQL查询

select count ( distinct w.processno ) AS "Number of Processes", y.userid from upmfolder f, upmperson p, w2process w, w2processcheck y where f.personid = p.personid and f.folderid = w.keynumb and w.Processno = y.processid and w.keyobject ='UPMFolder' group by 2

和另一个类似的是：

select count ( distinct w.processno ) AS "Number of Processes", y.userid from upmfolder f, upmperson p, w2process w, w2processcheck y where f.personid = p.personid and f.payrollmemberid = w.keynumb and w.keyobject = 'UPMPayrollmember' and w.Processno = y.processid group by 2

如何将两者合并为一个查询？所以计数和组仍然可以正常运行。我尝试使用union all，但这不起作用。我需要做什么？

Answer 1

您可以使用条件聚合执行此操作。对于count(distinct)，您需要提供NULL值：

select y.userid,
       count(distinct case when w.keyobject ='UPMFolder' then w.processno end) as NumFolder, 
       count(distinct case when w.keyobject ='UPMPayrollMember' then w.processno end) as NumPayrollMember
from upmfolder f, upmperson p, w2process w, w2processcheck y
where f.personid = p.personid and
      f.folderid = w.keynumb and
      w.Processno = y.processid
group by y.userid

注意：您还应该学习现代join语法。我没有更改查询，但是连接条件应该在on子句中，而不是在where子句中。

在SQL查询中一起使用count和union

1 个答案: