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oracle表间多字段连接

oracle表间多字段连接
 
问题如下:
SELECT *
  FROM table1 a, table2 b,
 WHERE a.1 = b.1
   AND a.2 = b.2
   AND a.3 = b.3
   ----------

 

   初始 a表里有数据  b表里是空的 想用a的那三个字段联合起来 join b 的那三个字段
方法1:
select * from 
table1 left outer join table2
on a.1=b.1 and a.2=b.2 and  a.3=b.3
方法2:
<!--StartFragment -->
SELECT a.*
  FROM table1 a, table2 b,
 WHERE a.1 = b.1(+)
   AND a.2 = b.2(+)
   AND a.3 = b.3(+)
方法3:
<!--StartFragment -->
a.1||a.2||a.3做主键

 

b也同样处理,然后再外连接
SELECT a.*
  FROM (select a.1||a.2||a.3 al from table1) a, (select b.1||b.2||b.3 bl from table2) b,
 WHERE a.al = b.bl(+)

 

 
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