显示一个表中的所有记录，并显示另一个表中的匹配记录

Question

Hi I have a tables below that has records of activites and points

Activites
|A_ID   |Site        | ActivityValue| ActivityName
 ---------------------------------------------------
|1      | site1      | 7             | ActivityName1
|2      | site1      | 6             | ActivityName2
|2      | site1      | 6             | ActivityName3
|2      | site1      | 6             | ActivityName4  



pointsTable
|UserID |RemainderPoints  | Active         | ActivityName |
------------------------------------------------------
|1      | 10              | TRUE           | ActivityName1| 
|2      | 5               | TRUE           | ActivityName2| 
|2      | 5               | TRUE           | ActivityName3| 
|2      | 5               | TRUE           | ActivityName3|  

what I need is return all records from Activities

SELECT  ActivityName FROM activity WHERE `Site`='Site1' 

Returns

ActivityName1
ActivityName2
ActivityName3
ActivityName4    

Then I need to sum user points based on user id from pointstable

SELECT UserID, ActivityName, Active,  SUM( RemainderPoints) 
FROM pointstable
WHERE UserID =2
AND Active =  'TRUE'  GROUP BY ActivityName    

Returns

|UserID |RemainderPoints   | Active         | ActivityName |
-------------------------------------------------------------
|2      | 5                | TRUE           | ActivityName2| 
|2      | 10               | TRUE           | ActivityName3|    

All that's fine separately but I need them put together for the user ie

ActivityName1  = 0
ActivityName2  = 5
ActivityName3  =10
ActivityName4  = 0

Any pointers?

Answer 1

Use an outer join:

select 
    a.activityName, 
    coalesce(sum(pt.remainderPoints), 0) points
from 
    activities a left outer join pointsTable pt on 
        pt.activityName = a.activityName and pt.UserID = 2
group by a.activityName

or a subquery:

select
    activities.ActivityName,
    coalesce(
        (select sum(RemainderPoints) from pointsTable where pointsTable.UserId = 2 and pointsTable.ActivityName = activities.ActivityName)
    , 0) points
from
    activities

Answer 2

SELECT a.ActivityName,SUM( p.RemainderPoints) FROM activity a left join pointstable p on a.ActivityName =p.ActivityName WHERE p.UserID =2 AND p.Active = 'TRUE' and a.site ='Site1' GROUP BY a.ActivityName

希望这可以帮助！