DB2SQL左联接表帮助

我有这样一个sql查询

    select 
    t1.id as ID,
    case when t2.field1 = 1102 then (t2.field3 - t2.field2) end as A,
    case when t2.field1 = 1112 then (t2.field3 - t2.field2) end as B,
    case when t2.field1 = 1113 then (t2.field3 - t2.field2) end as C,
    case when t2.field1 = 1106 then (t2.field3 - t2.field2) end as D 
   from table1 t1
   left join table2 t2
    on t1.id = t2.id

结果是这样的,

 ID   A      B     C     D
 ---- ------ ----- ----- ------
 1773 100    NULL  NULL   NULL
 1773 NULL   120   NULL   NULL
 1773 NULL   NULL  200    NULL
 1773 NULL   NULL  NULL   60

     ID   A      B     C     D
     ---- ------ ----- ----- ------
     1773 100    120   200   60

但我想展示这样的结果

 ID   A      B     C     D
 ---- ------ ----- ----- ------
 1773 100    NULL  NULL   NULL
 1773 NULL   120   NULL   NULL
 1773 NULL   NULL  200    NULL
 1773 NULL   NULL  NULL   60

     ID   A      B     C     D
     ---- ------ ----- ----- ------
     1773 100    120   200   60

---

如何重写查询？谢谢您的帮助。

每个值的嵌套查询如何

select t1.id as ID,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1102 ) as A,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1112 ) as B,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1113 ) as C,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1106 ) as D,     
from table1 t1

---

这远不是最优的，但它可以工作

对每个值进行嵌套查询怎么样

select t1.id as ID,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1102 ) as A,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1112 ) as B,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1113 ) as C,     
  (select t2.field3 - t2.field2 from table2 t2 
     where t1.id = t2.id and t2.field1 = 1106 ) as D,     
from table1 t1

这远不是最优的，但它可以工作

只需使用

sum（）

和

按id分组

即可：

select 
t1.id as ID,
sum(case when t2.field1 = 1102 then (t2.field3 - t2.field2) end) as A,
sum(case when t2.field1 = 1112 then (t2.field3 - t2.field2) end) as B,
sum(case when t2.field1 = 1113 then (t2.field3 - t2.field2) end) as C,
sum(case when t2.field1 = 1106 then (t2.field3 - t2.field2) end) as D 
from table1 t1
left join table2 t2 on t1.id = t2.id
group by 1;

效率高。易于理解的顺便说一句，

max（）

或

min（）

也同样适用

这是因为您的数据对于每个字段只有一次非空值；任何聚合函数都可以从空值中选择一个值。

只需使用

sum（）

和

按id分组即可将其展平：

select 
t1.id as ID,
sum(case when t2.field1 = 1102 then (t2.field3 - t2.field2) end) as A,
sum(case when t2.field1 = 1112 then (t2.field3 - t2.field2) end) as B,
sum(case when t2.field1 = 1113 then (t2.field3 - t2.field2) end) as C,
sum(case when t2.field1 = 1106 then (t2.field3 - t2.field2) end) as D 
from table1 t1
left join table2 t2 on t1.id = t2.id
group by 1;

效率高。易于理解的顺便说一句，
max（）
或
min（）
也同样适用

这是因为您的数据对于每个字段只有一次非空值；任何聚合函数都可以从空值中选择一个值。
所有行是否具有相同的ID？所有行是否具有相同的ID？