需要消除连接和联合中的欺骗

Question

谁能帮我解决这个问题

query::
select Ext_Acct,date_opened,last_date_flown,Sender from
table1 T1,table2 T2
where T1.Ext_acct(+)=T2.Ext_acct
union
select Ext_Acct,date_opened,last_date_flown,Sender from
table1 T1,table2 T3
where T1.Ext_acct(+)=T3.Ext_acct

我有数据::

表 1

Ext_Acct    date opened last date flown
AAA dd/mm/yyyy  dd/mm/yyyy
BBB dd/mm/yyyy  dd/mm/yyyy
CCC dd/mm/yyyy  dd/mm/yyyy

表 2

Ext_Acct    Sender  
AAA XXX

表 3

Ext_Acct    Sender  
BBB YYY 
CCC XXX

预期结果::

Ext Acct    date opened last date flown Sender
AAA dd/mm/yyyy  dd/mm/yyy   XXX
BBB dd/mm/yyyy  dd/mm/yyy   YYY
CCC dd/mm/yyyy  dd/mm/yyy   XXX

得到结果::

Ext Acct    date opened last date flown Sender
AAA dd/mm/yyyy  dd/mm/yyy   XXX
AAA         
BBB dd/mm/yyyy  dd/mm/yyy   YYY
BBB         
CCC dd/mm/yyyy  dd/mm/yyy   XXX
CCC

Answer 1

尝试在 T2 和 T3 上合并

select t1.Ext_Acct,
        t1.date_opened,
        t1.last_date_flown,
        t2.Sender 
from
      table1 T1,
       (select Ext_Acct, Sender from Table2 
        union 
        select Ext_Acct, Sender from Table3) T2
where T1.Ext_Acct=T2.Ext_Acct(+)

Answer 2

你可以试试 DISTINCT

select DISTINCT T1.Ext_Acct,T1.date_opened,T1.last_date_flown,T2.Sender from
table1 T1,table2 T2
where T1.Ext_acct(+)=T2.Ext_acct
union
select T1.Ext_Acct,T1.date_opened,T1.last_date_flown,T3.Sender from
table1 T1,table2 T3
where T1.Ext_acct(+)=T3.Ext_acct

但我建议不要使用 IMPLICIT JOINS 并开始使用 EXPLICIT JOINS，因为它在有大量数据时更准确。

SELECT DISTINCT T1.Ext_Acct,T1.date_opened,T1.last_date_flown,T2.Sender 
FROM TABLE1 T1 RIGHT JOIN TABLE2 T2
ON T1.Ext_acct = T2.Ext_acct
UNION
SELECT  T1.Ext_Acct,T1.date_opened,T1.last_date_flown,T3.Sender 
FROM TABLE1 T1 RIGHT JOIN TABLE3 T3
ON T1.Ext_acct = T3.Ext_acct

需要消除连接和联合中的欺骗

need to eliminate dupe in joins and union

oracle

union

outer-join