分组时避免多个子选择

Question

我有一个查询，其工作方式如下：

select table_one.x, sum(table_one.y)
(select foo from table_two where table_one.x = table_two.x) as item_description
from table_one
inner join table_two
on table_one.x = table_two.x
-- where table_2 row has various attributes
group by table_one.x

分组意味着我需要一个子选择来访问表二中的 foo。 现在，如果我想从表二中选择第二列，有没有办法在没有第二个子选择的情况下访问它？

数据库是 DB2。

编辑：join 是多对一的，即将 table_one 视为订单，将 table_b 视为包含该项目的信息。

Answer 1

table_two 对每个 table_one.x 是否有多行或者是一对二连接...如果是一对二连接，那么这是否不符合您的要求...因为您的子选择是在与您的加入条件相同

SELECT
   table_one.x, table_two.foo, sum(table_one.y)
FROM table_one
   INNER JOIN table_two
       ON table_one.x = table_two.x 
GROUP BY
   table_one.x, table_two.foo

Answer 2

SELECT  *
FROM    (
        SELECT  x, SUM(y)
        FROM    table_one
        GROUP BY
                x
        ) AS t1
INNER JOIN
        table_two t2
ON      t2.x = t1.x
-- where table_2 row has various attributes