多个表上的SQL LEFT JOIN

Question

给出三个表：

1. Account
   1. UniqueID
   2. Account Group
2. VR
   1. UniqueID
   2. AccountID
3. CR
   1. UniqueID
   2. AccountID

AccountID中的VR和CR中的UniqueID引用Account中的Account。

我想获得一个结果，该结果显示第一列中的Account Account组和VR组Account中的数据量第二列，最后是第3列中每CR组的数据量SELECT account_group AS 'Account Group', COUNT(Account.AccountId) AS 'Anzahl Accounts', COUNT(VR.ActivityId) AS 'VR', COUNT(Contact.ContactId) AS 'Contact' FROM [MSCRM].[dbo].[AccountBase] LEFT JOIN MSCRM.dbo.visit_report_activityBase ON Account.AccountId = VR.account_id LEFT JOIN MSCRM.dbo.ContactBase ON Account.AccountId = Contact.ParentCustomerId GROUP BY account_group ORDER BY account_group ASC; 。

实施这种联接的正确方法是什么？

我的尝试：

COUNT(*)

但没有COUNT显示我想要的实际金额。

即使Account.AccountId {{1}}显示的号码无效。

Answer 1

我相信你要找的东西是不同的：

SELECT account_group as 'Account Group',
       count(distinct Account.AccountId) as 'Anzahl Accounts',
       count(distinct VR.ActivityId) as 'VR' count(distinct Contact.ContactId) as 'Contact'
  FROM [ MSCRM ] . [ dbo ] . [ AccountBase ] as Account
  left join MSCRM.dbo.visit_report_activityBase as VR
    on Account.AccountId = VR.account_id
  left join MSCRM.dbo.ContactBase as Contact
    on Account.AccountId = Contact.ParentCustomerId
 group by account_group
 order by account_group