最佳的方式共同

Question

什么是此查询结婚在一起的最佳方式：

SELECT apvr.LIMIT, apvr.APPROVER_ID, usr.IS_ACTIVE, usr.USER_FULL_NAME   
FROM APPROVERS apvr, USER usr 
WHERE apvr.APPROVER_ID = usr.ID 

这一个：

SELECT usr.USER_FULL_NAME, COUNT(*) as numOfApprovals, MAX(APPROVAL_DATE) as lastApprovalDate  
FROM IM_APPROVAL_DETAIL appd, USER usr 
WHERE usr.ID = appd.APPROVER_ID 
GROUP By usr.USER_FULL_NAME 

？

Answer 1

没有真实的数据可能会有点辛苦，但我的建议是以下几点：

SELECT apvr.LIMIT, apvr.APPROVER_ID, usr.IS_ACTIVE, usr.USER_FULL_NAME, count(*) as numOfApprovals, max(appd.approval_date) as lastApprovalDate 
FROM APPROVERS apvr 
JOIN USER usr ON apvr.APPROVER_ID = usr.ID 
JOIN IM_APPROVAL_DETAIL appd ON usr.ID = appd.APPROVER_ID 
GROUP By apvr.Approver_ID; 

，因为我不知道这些表中的reoccurances的有可能BY子句一些问题与组。因此，另一种方法是使用一个子选择：

SELECT apvr.LIMIT, apvr.APPROVER_ID, usr.IS_ACTIVE, usr.USER_FULL_NAME, appd.numOfApprovals, appd.lastApprovalDate 
FROM APPROVERS apvr 
JOIN USER usr ON apvr.APPROVER_ID = usr.ID 
JOIN IM_APPROVAL_DETAIL appd 
JOIN (
    SELECT approver_id id, count(*) numOfApprovals, max(approval_date) lastApprovalDate 
    FROM im_approval_detail 
    GROUP by id) appd 
ON appd.id = usr.ID