ORA-00918: column ambiguously defined错误应对方法
最近做一个项目，经常需要用到多表查询，通过需要分页等，于是经常会碰到
ORA-00918: column ambiguously defined错误应对方法，意思是说，某一列定义模糊，于是
经过了很多方面的测试，总算能解决，尤其是在涉及到tablename.*，这里的*很容易出现这样的错误。
需要仔细的研究下面的2个sql语句：
select v1.*,(v1.data-v2.data) as rate, v3.*, (v3.data-v4.data) as rate2
from (
select rownum as rn, a.* from (
select ayearmon, DATA, DATA-100 as rate
from test
where isvalid=1 and code='3503'
and region = '000000'
order by ayearmon desc
) a) v1,
(
select (rownum-1) as rn1, b.* from (
select ayearmon, DATA
from test
where isvalid=1 and code='3503'
and region = '000000'
order by ayearmon desc
) b) v2,
( select rownum as rn, c.* from (
select ayearmon, DATA, DATA-100 as rate
from test
where isvalid=1 and code='3502'
and region = '000000'
order by ayearmon desc
) c) v3,
(
select (rownum-1) as rn1, d.* from (
select ayearmon, DATA
from test
where isvalid=1 and code='3502'
and region = '000000'
order by ayearmon desc
) d) v4
where v1.rn = v2.rn1 and v3.rn = v4.rn1 and v1.rn = v3.rn
and v1.rn >= 1 and v1.rn <= 10
和
select * from (
select v1.*, CASE WHEN substr(v1.ayearmon, 5, 2) = '02' THEN v1.DATA ELSE (v1.DATA - v2.DATA) END as dy
from (
select rownum as rn, a.* from (
select ayearmon, DATA
from v_yy_MAC201
where isvalid=1 and code='10011001' and length(ayearmon) = 6
and timetype='b0301' and region = '000000'
order by ayearmon desc
) a) v1,
(
select (rownum-1) as rn1, b.* from (
select ayearmon, DATA
from v_yy_MAC201
where isvalid=1 and code='10011001' and length(ayearmon) = 6
and timetype='b0301' and region = '000000'
order by ayearmon desc
) b) v2 where v1.rn = v2.rn1
)
where rn >= 1 and rn <= 50
通过上面的2个sql，能不能发现什么规律呢？
有空继续讨论。