SQL - 使用 LEFT OUTER JOIN 计数不正确

Question

我正在尝试从问题表中检索字段以及来自评论表和 issue_assigneduser 表的相关记录计数。如果有 2 条评论和 6 个分配的用户，我返回的两个计数的值都是 12。知道如何解决这个问题吗？

SELECT issue.issueid, COUNT(comment.commentid) AS CountOfComments, 
    Count(issue_assigneduser.userid) as CountOfAssignedUsers, 
    issue.title, issue.detail, issue.enteredby, 
    issue.datetimeentered, issue.assignedto, issue.categoryid,  
    issue.severityid, issue.statusid, 
    issue.lastcommentdatetime as LastCommentDateTime, 
    issue.lastcommentbyuserid, 
    users.initials as LastCommentUserInitials,  
    lookupstatus.status as Status, 
    lookupcategory.category as Category, 
    lookupseverity.severity as Severity, 
    GetUTCDate() as UTCDateTime  
FROM issue
    INNER JOIN lookupcategory ON issue.categoryid = lookupcategory.categoryid
    INNER JOIN lookupseverity ON issue.severityid = lookupseverity.severityid
    INNER JOIN lookupstatus ON issue.statusid = lookupstatus.statusid
    LEFT OUTER JOIN  comment ON issue.issueid = comment.issueid
    LEFT OUTER JOIN  issue_assigneduser ON issue.issueid = issue_assigneduser.issueid
    LEFT OUTER JOIN  users ON issue.lastcommentbyuserid = users.userid  
GROUP BY issue.issueid, issue.title, issue.detail, 
    issue.enteredby, issue.datetimeentered, 
    issue.assignedto, issue.categoryid, 
    issue.severityid, issue.statusid,  
    issue.lastcommentdatetime, 
    issue.lastcommentbyuserid, 
    users.initials, lookupstatus.status, 
    lookupcategory.category, 
    lookupseverity.severityid, users.initials, 
    lookupstatus.status, lookupcategory.category, 
    lookupseverity.severity  
ORDER BY issue.lastcommentdatetime DESC;

Answer 1

使用 COUNT( DISTINCT fieldname )而不是 COUNT ( fieldname )
例如对于用户

Count(DISTINCT issue_assigneduser.userid) as CountOfAssignedUsers