Sql 基于列值获取活动记录

我有一个名为BusinessAssociate的数据库表，出于复杂性考虑，该表中有两列

BusinessAssociateKey int
AmalgamatedIntoBAKey int

使用BusinessAssociateKey，我们可以加入其他表，其中一个表（BACorporateStatus）告诉我们该BusinessAssociateKey是活动的还是合并的

假设业务关联键123456合并到BA键987654中，在同一个表中会有一行，BusinessAssociateKey为987654，这一行也可能合并到BusinessAssociateKey 283746中

在per BusinessAssociateKey上是否有办法找到活跃（非合并）的业务伙伴

链的数量未知，可能为无，也可能为n

编辑：这是一个SQL FIDLE，在本例中，BusinessAssociateKey 56781未合并，因此对于BusinessAssociateKey 123，幸存/活动BA键为56781。

递归：

;with rec_cte as(
select b1.BusinessAssociateKey, b1.AmalgamatedIntoBAKey, 1 as rn
  from BusinessAssociate b1 left outer join BusinessAssociate b2 on b1.BusinessAssociateKey = b2.AmalgamatedIntoBAKey
  where b2.BusinessAssociateKey is null
union all
select c.BusinessAssociateKey, b.AmalgamatedIntoBAKey, c.rn + 1
  from rec_cte c inner join BusinessAssociate b on c.AmalgamatedIntoBAKey = b.BusinessAssociateKey
  where b.AmalgamatedIntoBAKey is not null),
cte as(
select BusinessAssociateKey, max(rn) as rn
  from rec_cte
  group by BusinessAssociateKey)

select r.BusinessAssociateKey, r.AmalgamatedIntoBAKey
  from rec_cte r inner join cte c on r.BusinessAssociateKey = c.BusinessAssociateKey and r.rn = c.rn
  option (maxdop 0)

---

与表进行自联接。在这里，我添加了行号，以使用自联接获取最后的记录

   Select  F.Nbr, F.BusinessAssociateKey, F.AmalgamatedIntoBAKey
    From
   (Select row_number() Over(order by (select 1)) as Nbr, E.BusinessAssociateKey, E.AmalgamatedIntoBAKey
    From BusinessAssociate E
   ) F
   LEFT OUTER JOIN
   (Select row_number() Over(order by (select 1)) as Nbr, E.BusinessAssociateKey, E.AmalgamatedIntoBAKey
    From BusinessAssociate E
   ) K
   ON  F.AmalgamatedIntoBAKey = K.BusinessAssociateKey
   where K.Nbr IS  NULL 

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没错，但如果你看小提琴，比如说我的业务关联键是123，我想“走下”链条，得到最后一个激活的BA键Close，但我想要的结果是原来的BusinessAssociateKey（123），我想合并的键是56781