mysql - 如何使用两个SQL请求(mysql)计算平均数

Question

我想按项目计算重新开票的平均数量，但我无法通过单个 SQL 请求来做到这一点。 我已检索到门票总数:

select count(jiraissue.id) as totalTicketByProj
from jiraissue ,project
where jiraissue.project=project.id
group by project.pname;

我还检索了重新开票的数量:

select count(changeitem.id) as nbissueReopenByProject
from changeitem,changegroup,jiraissue,project
where changeitem.groupid=changegroup.id
and changegroup.issueid=jiraissue.id
and jiraissue.project= project.id
and changeitem.oldstring="Resolved"
and changeitem.newstring="Closed"
group by project.pname;

但我不知道如何使用单个请求计算重新打开的票证的平均数量(nbissueReopenByProject/totalTicketByProj)!!

任何想法!!

Answer 1

SELECT (nbissueReopenByProject / totalTicketByProj)
  FROM (SELECT project.pname, COUNT(jiraissue.id) AS totalTicketByProj
          FROM jiraissue, project
         WHERE jiraissue.project = project.id
         GROUP BY project.pname) ttbp,
       (SELECT project.pname, COUNT(changeitem.id) AS nbissueReopenByProject
          FROM changeitem, changegroup, jiraissue, project
         WHERE changeitem.groupid = changegroup.id
           AND changegroup.issueid = jiraissue.id
           AND jiraissue.project = project.id
           AND changeitem.oldstring = "Resolved"
           AND changeitem.newstring = "Closed"
         GROUP BY project.pname) nbirbp
 WHERE ttbp.pname = nbirbp.pname