SQL GROUP BY 涉及两个表

Question

你们能帮我SELECT查询我的简单案例吗：

Table A:        
UserID  UserName
10      John
11      Mike
12      Matt


Table B:            
SessionID   UserID  SessionTime
124         10      20
123         10      122
42          10      30
324         11      55
534         11      42
344         12      19
653         12      32

我需要这个结果：

Result Table:               
UserName    UserID  TotalTime
John        10      172
Mike        11      97
Matt        12      51

对于一个 Table B 这有效：

SELECT UserID, SUM(SessionTime) AS "Total Time"
FROM TableB
GROUP BY UserID;

但我需要将用户名附加到最终结果

谢谢

Answer 1

您可以通过使用加入和分组来做到这一点：

select a.UserId, a.UserName, sum(b.SessionTime) as TotalTime
from tableA a
left join tableB b on a.UserId = b.UserId
group by a.UserId, a.UserName;

注意：这适用于您的情况下的一对多关系。

Answer 2

SELECT TableA.Username, TableA.User_ID, SUM(SessionTime) INNER JOIN
TableB ON TableA.User_ID = TableB.User_ID GROUP BY TableA.Username,
TableA.User_ID

Answer 3

SELECT a.UserName as "UserName" 
      ,a.UserID as "UserID"
      ,sum(b.SessionTime) as "TotalTime" 
FROM a LEFT JOIN b 
ON a.UserID = b.UserID GROUP BY a.UserID

这里。我用了 TABLE a 和 Table b

SQL GROUP BY 涉及两个表

SQL GROUP BY with two tables involved

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