在Oracle中的多个表上进行左外连接

Question

如何编写一个oracle查询,它等同于informix中的以下查询:

select tab1.a,tab2.b,tab3.c,tab4.d 
  from table1 tab1,
       table2 tab2 OUTER (table3 tab3,table4 tab4,table5 tab5) 
 where tab3.xya = tab4.xya 
   AND tab4.ss = tab1.ss 
   AND tab3.dd = tab5.dd 
   AND tab1.fg = tab2.fg 
   AND tab4.kk = tab5.kk 
   AND tab3.desc = "XYZ"

我试过:

select tab1.a,tab2.b,tab3.c,tab4.d 
  from table1 tab1,
       table2 tab2 LEFT OUTER JOIN (table3 tab3,table4 tab4,table5 tab5) 
 where tab3.xya = tab4.xya 
   AND tab4.ss = tab1.ss 
   AND tab3.dd = tab5.dd 
   AND tab1.fg = tab2.fg 
   AND tab4.kk = tab5.kk 
   AND tab3.desc = "XYZ"

任何人都可以帮助我获得正确的语法.

Answer 1

每个连接写一个表,如下所示:

select tab1.a,tab2.b,tab3.c,tab4.d 
from 
  table1 tab1
  inner join table2 tab2 on tab2.fg = tab1.fg
  left join table3 tab3 on tab3.xxx = tab1.xxx
  left join table4 tab4 on tab4.xya = tab3.xya and tab4.ss = tab3.ss
  left join table5 tab5 on tab5.dd = tab3.dd and tab5.kk = tab4.kk
where
  tab3.desc = "XYZ"

请注意,虽然我的查询包含实际的左连接,但您的查询显然没有.由于条件在where,您的查询应该像内部联接一样.(虽然我承认我不知道Informix,所以也许我错了).

如果确实如此,您可以将左连接更改为内连接.您应尽可能使用内连接,因为它们比左连接更快.

PS:左连接和左外连接是相同的.

Answer 2

我猜你想要的东西

SELECT tab1.a, tab2.b, tab3.c, tab4.d
  FROM table1 tab1 
       JOIN table2 tab2 ON (tab1.fg = tab2.fg)
       LEFT OUTER JOIN table4 tab4 ON (tab1.ss = tab4.ss)
       LEFT OUTER JOIN table3 tab3 ON (tab4.xya = tab3.xya and tab3.desc = 'XYZ')
       LEFT OUTER JOIN table5 tab5 on (tab4.kk = tab5.kk AND
                                       tab3.dd = tab5.dd)