sql - 只需要从 INNER JOIN 返回一行

Question

我只想从内部联接返回第一行。我有两个表:

TABLE_X |  TABLE_Y
id      |  id   creationdate  xid 
1       |  1    01/01/2011    1
2       |  2    01/01/2011    1
3       |  3    31/12/2010    2
4       |  4    28/12/2010    3

表 Y 中的行可以具有相同的创建日期，因此我首先从该集合中获取 MAX(creationdate)，然后获取 MAX(id)，例如:

SELECT  a.id,
        c.id,
        d.id,
        e.id,
        d.CREATIONDATE,
        a.REFNUMBER,
        a.DATECREATED,
        a.DESCRIPTION,
        e.CATEGORYCODE,
        e.OUTSTANDINGAM_MONAMT,
        e.PREVPAIDAMOUN_MONAMT,
        e.TOTALINCURRED_MONAMT,
        e.LOSSFROMDATE,
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
         )
      )
   )
)

这在我自己调用它时有效，但是当我将它添加到 INNER JOIN 时，我为表 Y 中的每个匹配行获取一行。

我想要的是来自 TABLE_X 的创建日期和 id 的最新记录，其中 xid = id。

Answer 1

试试这个查询

select *,(
select top 1 creationdate from Table_Y 
where from Table_Y.xId = m.id
order by Table_Y.CreationDate 
) 
from Table_X m

子查询将选择具有最大创建日期的前 1 个结果，主查询将选择所有记录，以便您获得所需的结果