具有最小和最大记录的 db2 递归

Question

我们需要 table :

drop table relations; 
create table relations (OLD_GID varchar(60), NEW_GID varchar(60)); 
insert into relations values('GID5','GID4'); 
insert into relations values('GID4','GID3'); 
insert into relations values('GID2','GID1'); 
insert into relations values('GID3','GID2'); 
insert into relations values('GID10','GID11'); 
insert into relations values('GID20','GID21'); 
insert into relations values('GID30','GID32'); 
insert into relations values('GID31','GID32'); 
insert into relations values('GID40','GID42'); 
insert into relations values('GID41','GID42'); insert into relations values('GID42','GID43');

以这样的table结尾

OLD_GID                                             NEW_GID           

------------------------------------------------------------
GID5                                                GID1  
GID4                                                GID1  
GID3                                                GID1 
GID2                                                GID1

GID40                                               GID43 
GID41                                               GID43 
GID42                                               GID43

GID10                                               GID11

GID20                                               GID21

GID30                                               GID32 
GID31                                               GID32

意义如果我有： Gid1 父亲是 Gid2 Gid2 的父亲是 Gid3

那么输出将是

Gid1 与所有 Gid3 之父 Gid2 与 Gid3 之父

我开始写这个查询但是我卡住了

WITH RPL (OLD_GID, NEW_GID) AS
     (  SELECT ROOT.OLD_GID, ROOT.NEW_GID
        FROM relations ROOT
        WHERE ROOT.OLD_GID in ( select OLD_GID from relations where OLD_GID  not in ( select NEW_GID from relations ))
      UNION ALL
        SELECT CHILD.OLD_GID, CHILD.NEW_GID
        FROM RPL PARENT, relations CHILD
        WHERE  PARENT.NEW_GID = CHILD.OLD_GID
     )
select --  row_number() over(order by 1) as genkeycol  , OLD_GID, NEW_GID
        OLD_GID, NEW_GID
from RPL

谢谢 -

Answer 1

试试这个：

WITH T (OLD_GID, NEW_GID) AS
(
  SELECT *
  FROM RELATIONS P
  WHERE NOT EXISTS (SELECT 1 FROM RELATIONS C WHERE C.OLD_GID = P.NEW_GID)
    UNION ALL
  SELECT R.OLD_GID, T.NEW_GID
  FROM RELATIONS R, T
  WHERE R.NEW_GID = T.OLD_GID
)
SELECT * 
FROM T
ORDER BY NEW_GID, OLD_GID

结果是：

OLD_GID	NEW_GID
GID2	GID1
GID3	GID1
GID4	GID1
GID5	GID1
GID10	GID11
GID20	GID21
GID30	GID32
GID31	GID32
GID40	GID43
GID41	GID43
GID42	GID43

具有最小和最大记录的 db2 递归

db2 Recursive with min and max records

db2

db2-400