oracle表间多字段连接

SELECT *
  FROM table1 a, table2 b,
 WHERE a.1 = b.1
   AND a.2 = b.2
   AND a.3 = b.3
   ----------

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：
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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：
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a.1||a.2||a.3做主键

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(+)