Mysql Distinct Sum Aggregation On Join 操作

Question

我有一个如下查询：

Select t1.field1
     , sum(t2.field2)
     , sum(t3.field3) 
  from table1 t1
  left 
  join table2 t2 
    on t1.field1 = t2.field1
  left 
  join table3 t3  
    on t2.field1 = t3.field1 
   and t2.date = t3.date
group by t1.field1;

假设表格内容如下所示：

table1:
-field1-
  test
  test1
  test2     

table2:
-field1- -field2- -date-
  test      5       0
  test      4       1
  test      3       2
  test1     3       2

table3:
-field1- -field3- -date-
  test      1       0
  test      2       1
  test      3       2
  test      3       3
  test      3       4
  test      3       5

当我运行查询时，查询会给出结果：

-field1-   -sum(field2)-  -sum(field3)-
  test          24              15
  test1         3              null
  test2        null            null  

这里的问题； sum(field2) 包含来自左连接操作的重复值。我想根据不同 table2 field2 值的总和显示 sum(field2) 。 所以我想得到结果：

-field1-   -sum(field2)-  -sum(field3)-
  test          12              15
  test1         3              null
  test2        null            null  

注意：请不要向我建议派生表选项，因为我知道这可以通过派生表来解决（左联接（从表 3 中选择...按字段 1、字段 2 分组））。

Answer 1

试试下面这个选项-

SELECT A.field1,B.field2,C.field3 
FROM Table1 A
LEFT JOIN (
    SELECT field1,SUM(field2) field2 
    FROM Table2 GROUP BY field1
)B ON A.field1 = B.field1
LEFT JOIN (
    SELECT field1,SUM(field3) field3 
    FROM Table3 GROUP BY field1
)C ON A.field1 = C.field1

Answer 2

预聚合结果：

select t1.field1, t2.sum2, t3.sum3
from table1 t1 left join
     (select t2.field1, sum(t2.field2) as sum2
      from table2 t2 
      group by t2.field1
     ) t2
     on t1.field1 = t2.field1 left join
     (select t3.field1, sum(t3.field3) as sum3
      from table3 t3 join
           table2 t2
           on t2.field1 = t3.field1 and t2.date = t3.date
      group by t3.field1
     ) t3
     on t3.field1 = t1.field1;

这很棘手，因为date 的条件介于 table2 和 table3 之间。

您指定的期望结果似乎没有考虑date，这在一定程度上简化了逻辑：

select t1.field1, t2.sum2, t3.sum3
from table1 t1 left join
     (select t2.field1, sum(t2.field2) as sum2
      from table2 t2 
      group by t2.field1
     ) t2
     on t1.field1 = t2.field1 left join
     (select t3.field1, sum(t3.field3) as sum3
      from table3 t3
      group by t3.field1
     ) t3
     on t3.field1 = t1.field1;