Question

假设我们有三个表

T1

 ID |Type| Class | Points
 111|1   |a101   | 12
 111|1   |b104   | 10
 112|2   |a112   | 40
 118|1   |a245   | 30
 186|2   |c582   | 23

T2（Type = 1的数据）

 ID |Type|EPoints
 111|1   |4
 118|1   |3

T3（Type = 2的数据）

 ID |Type|EPoints
 112|2   |9
 186|2   |15

我们希望有一个View，它将显示ID，Type，sum（Points）+ Epoints 例如

 ID |Type| Points
 111|1   | 26
 112|2   | 49
 118|1   | 33
 186|2   | 38

我该怎么做？

Answer 1

select dt.id
     , dt.type
     , dt.points + coalesce(t2.epoints, t3.epoints) as points
  from (select t1.id
             , t1.type
             , sum(t1.points) as points
          from t1
        group
            by t1.id) as dt
left outer
  join t2
    on t2.type = dt.type
left outer
  join t3
    on t3.type = dt.type

Answer 2

看起来这可能有用（连接可能需要左边一个 - 使用围绕Epoints的COALESCE将空值转换为零 - 如果你需要对t1中的记录采取预防措施而没有任何匹配的记录当然，在其他任何一个表中。

SELECT t1.ID, t1.Type, SUM(t1.Points) + other.Epoints
FROM t1
JOIN (
  t2
  UNION
  t3
) other ON (other.Type = t1.Type)
GROUP BY t1.ID

来自不同表的组和总和

2 个答案: