入門基於活動記錄的列值

Question

我有一個名爲BusinessAssociate一個數據庫表，該表中對複雜的緣故有2列

BusinessAssociateKey int 
AmalgamatedIntoBAKey int 

使用，我們可以加入其它表的BusinessAssociateKey，和一個這些表（BACorporateStatus）告訴我們該BusinessAssociate是活動還是合併。

讓我們假設業務助理鍵123456被合併到BA的關鍵987654，在同一個表會出現一排，用987654一BusinessAssociateKey，而該行很可能是過於合併，例如進入BusinessAssociateKey 283746.

是否有每個BusinessAssociateKey找到活動（未合併）業務夥伴的方法？

鏈的數目是未知的，可能是沒有或可能是n。

編輯：這是一個SQL小提琴，http://sqlfiddle.com/#!9/1e886/1在這個例子中BusinessAssociateKey 56781沒有合併，所以BusinessAssociateKey 123尚存/主動BA關鍵是56781.

Answer 1

遞歸：

;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) 

Answer 2

待辦事項與桌子自我加入。在這裏，我添加了行號以使用自連接來獲取最後的記錄。

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 

http://sqlfiddle.com/#!6/88b53/26