Question

以下查询返回重复/多条记录。有没有一种方法可以对SW.MTableId的不同ID进行第二次左联接。

SELECT SW.* from
(SELECT * FROM Stable SD,MTable MT WHERE SD.ID=1234 AND SD.ID=MT.Stable_ID) SW  
LEFT OUTER JOIN TTable TD ON (TD.MTable_ID=SW.MTableId AND TD.STATUS='ACTIVE') 
LEFT OUTER JOIN PTable PT ON (PT.MTable_ID=SW.MTableId AND PT.TTable_ID IS NULL) 
enter code here

重复的行：

SW.MTableId TD.MTable_ID  PT.MTable_ID 
71878        67048         849230
71878        67046         849230
71878        67047         849230
71878        67039         849230
71878        67038         849230
71878        67045         849230
71878        67037         849230

http://sqlfiddle.com/#!9/5a127b/2创建了带有完整表定义的小提琴，要求我们需要执行查询才能从每个表中获取主键列。

Stable can be direct parent of Ftable, Ttable, Etable, Rtable.
Ftable can be direct parent of Ttable, Etable only.
Ttable can be direct parent of Etable, Rtable.
Etable can be direct parent of Rtable.

＃预期结果

Sid  Fid  Tid  Eid  Rid
2    12   103  203  303
2    12   103  203  304
1    null 101  null 302 
3    null null null 301
1    10   null 202  null
1    null null 201  null  
1    null 102  null null
1    11   null null

Stable
sid, sname
1,   'S1'
2,   's2'
3,   's3'

Ftable
fid, fname, sid
10,  'f1',  1
11,  'f2',  1
12,  'f3',  2

Ttable
tid, tname, fid,  sid
101, 't1',  null, 1
102, 't2',  null, 1
103, 't3',  12,   2

Etable
eid, ename, tid , fid, sid
201, 'e1',  null, null, 1
202, 'e2',  null, 10,   1
203, 'e3',  103,  12,   2

Rtable 
(rid, rname eid  tid  sid)
(301, 'r1'  null null 3) 
(302, 'r2'  null 101  1)
(304, 'r4'  203, 103  2)
(303, 'r3'  203, 103  2)

Answer 1

您希望rtable的所有行和etable的所有行。
您希望ttable中的那些行在前两个表中不匹配。
您希望ftable中的那些行在前三个表中不匹配。
您希望稳定的那些行在前四个表中不匹配。

您认为null为值，即您认为null = null是匹配项。

这是逐步进行查询的查询。

select sid, null as fid, tid, eid, rid from rtable
union all
select sid, fid, tid, eid, null as rid from etable
union all
select sid, fid, tid, null as eid, null as rid from ttable
  where (sid, coalesce(fid, -1), coalesce(tid, -1)) not in 
    (select sid, coalesce(fid, -1), coalesce(tid, -1) from etable)
  and (sid, coalesce(fid, -1), coalesce(tid, -1)) not in 
    (select sid, -1, coalesce(tid, -1) from rtable)
union all
select sid, fid, null as tid, null as eid, null as rid from ftable
  where (sid, coalesce(fid, -1)) not in
    (select sid, coalesce(fid, -1) from ttable)
  and (sid, coalesce(fid, -1)) not in
    (select sid, coalesce(fid, -1) from etable)
  and (sid, coalesce(fid, -1)) not in
    (select sid, -1 from rtable)
union all
select sid, null as fid, null as tid, null as eid, null as rid from stable
  where sid not in (select sid from ftable)
  and sid not in (select sid from ttable)
  and sid not in (select sid from etable)
  and sid not in (select sid from rtable)
order by sid, fid, tid, eid, rid;

结果几乎是您所要求的。只是，您将sid 2的rtable和etable行合并，但我不知道为什么。好吧，如果这是您的需要，则可以相应地更改我的查询。

演示：http://sqlfiddle.com/#!9/ae1a69/1

左外部联接返回多个记录

1 个答案: