查询中的计数、SUM、LEFT JOIN 和 GROUP BY 无法正常工作答案

【问题标题】：Count, SUM, LEFT JOIN and GROUP BY in query not working right查询中的计数、SUM、LEFT JOIN 和 GROUP BY 无法正常工作
【发布时间】：2014-10-27 15:16:20
【问题描述】：

我已经尝试了一些方法，但我似乎无法找出导致问题的原因。当我删除 totalHours 部分时，查询工作正常。但有了它，它会显示正确的小时数，但会显示错误的工作、选定和获胜者数量。

谁能告诉我我做错了什么？

提前致谢。

这是我的查询；

SELECT 

    crmCandidate.candidateID, 
    crmCandidate.candidateName, 

    COUNT(DISTINCT crmJoin.joinID) AS Jobs, 

    SUM(IF(crmJoin.joinExtra = 'select', 1, 0)) AS Selected, 
    SUM(IF(crmJoin.joinExtra = 'winner', 1, 0)) AS Winner, 

    ROUND(SUM(crmDays.total)) AS totalDays 

FROM crmCandidate 
LEFT JOIN crmJoin ON (crmJoin.joinChild = crmCandidate.candidateID) 
LEFT JOIN crmJob ON (crmJob.jobID = crmJoin.joinParent) 
LEFT JOIN crmDays ON (crmDays.dayCandidateID = crmJoin.joinChild) 

WHERE 

    crmDays.dayJobID = crmJob.jobID AND 
    crmDays.dayCandidateID = crmCandidate.candidateID 

GROUP BY 
    crmCandidate.candidateID 

ORDER BY DESC 

LIMIT 100

【问题讨论】：

crmhours 表连接丢失，示例数据和预期结果也会有所帮助
对不起，你是对的，我已经更新了我的查询。

标签： mysql count group-by sum left-join

【解决方案1】：

试试这个：

SELECT 
    crmCandidate.candidateID, 
    crmCandidate.candidateName, 
    COUNT(DISTINCT crmJoin.joinID) AS Jobs, 
    Sum(Case When crmJoin.joinExtra = 'select' Then 1 else 0 end) as Selected,
    Sum(Case When crmJoin.joinExtra = 'winner' Then 1 else 0 end) as winner,
    ROUND(SUM(crmDays.total)) AS totalDays 
FROM crmCandidate 
LEFT JOIN crmJoin   
    ON crmJoin.joinChild = crmCandidate.candidateID
LEFT JOIN crmJob    
    ON crmJob.jobID = crmJoin.joinParent
Inner JOIN crmDays  
    On  crmDays.dayCandidateID  = crmCandidate.candidateID 
    AND crmDays.dayJobID        = crmJob.jobID
GROUP BY crmCandidate.candidateID, crmCandidate.candidateName
ORDER BY candidateID DESC 
LIMIT 100

【讨论】：

【解决方案2】：

最好的办法是在您执行join 之前汇总数据。您可以使用以下count(distinct) 子句做您想做的事：

COUNT(DISTINCT case when crmJoin.joinExtra = 'select' then crmJoin.JoinId end) AS Selected, 
COUNT(DISTINCT case when crmJoin.joinExtra = 'winner' then crmJoin.JoinId end) AS Winner,

【讨论】：