sql - 在INNER JOIN上返回一行

Question

我只想从内部联接返回第一行。我有两个表：

TABLE_D和TABLE_E中的行可以具有相同的创建日期，因此我首先要从该集合中获取MAX（creationdate），然后是MAX（id）。这是我完整的查询：





SELECT
a.id as A_ID,
b.id as B_ID,
c.id as C_ID,
d.id as D_ID,
e.id as E_ID,
d.CREATIONDATE,
a.REFNUMBER,
a.DATECREATED,
a.INFO,
e.COST,
FROM 
TABLE_A a
INNER JOIN TABLE_B b ON (b.id = a.id)
INNER JOIN TABLE_C c ON (c.id = b.id)
INNER JOIN TABLE_D d ON
(
   c.i =
   (
      select
      d.id
      FROM TABLE_D
      WHERE TABLE_D.id = c.id
      AND TABLE_D.id =
      (
         select
         max(id)
         from TABLE_D t1
         where c_id = c.id
         and CREATIONDATE =
         (
            select
            max(CREATIONDATE)
            from TABLE_D t2
            where t2.c_id = t1.c_id
         )
      )
   ) 
)

INNER JOIN TABLE_E e ON
(
   d.i =
   (
      select
      e.d_id
      from TABLE_E
      where d_id = d.id
      AND id =
      (
         select
         max(id)
         from e t1
         where e.d_id = d.id
         and CREATIONDATE =
         (
            select
            max(CREATIONDATE)
            from TABLE_E t2
            where t2.d_id = t1.d_id
         )
      )
   )
)





我的子查询获取具有最大creationdate的所有行，并且当我单独调用它时，从其最大id可以正常工作，但是当我将其添加到INNER JOIN（见上文）时，表D中的每个匹配行都得到一行我想要的是每个TABLE_A.id的一行，仅显示TABLE_D与TABLE_C关联的最新行以及TABLE_E与TABLE_D关联的最新行。

例如，目前我的结果集中的ID如下所示：

--------------------------------------------------------------------------
A_ID            B_ID            C_ID            D_ID            E_ID
--------------------------------------------------------------------------
1               101             201             301             401
1               101             201             301             402    
1               101             201             301             403    
1               101             201             302             404
1               101             201             302             405    
1               101             201             302             406    

我需要的是：

--------------------------------------------------------------------------
A_ID            B_ID            C_ID            D_ID            E_ID
--------------------------------------------------------------------------
1               101             201             302             406

在此先感谢您的帮助。

Answer 1

使用oracle11g中可用的解析函数ROW_NUMBER（）

SELECT *
FROM 
(
SELECT
    a.id as A_ID,b.id as B_ID,c.id as C_ID,d.id as D_ID,e.id as E_ID,
    d.CREATIONDATE,a.REFNUMBER,a.DATECREATED,a.INFO,e.COST,
    row_number() over (
        partition by a.id, b.id, c.id
        order by d.CREATIONDATE DESC, d.id desc, e.CREATIONDATE DESC, e.id desc) RN
FROM TABLE_A a
INNER JOIN TABLE_B b ON (b.id = a.id)
INNER JOIN TABLE_C c ON (c.id = b.id)
INNER JOIN TABLE_D d ON d.c_id = c.id
INNER JOIN TABLE_E e ON e.d_id = d.id
) N
WHERE RN = 1

只要确保PARTITION和ORDER BY子句是正确的

partition by a.id, b.id, c.id
    => start numbering from 1 again when any one of these changes
order by d.CREATIONDATE DESC, d.id desc, e.CREATIONDATE DESC, e.id desc)
    => number the rows in this order