SQL错误：使用子查询模糊定义的列

Question

我正在尝试进行分页显示，之前我已经成功使用过这种模式，但是这个模式由于某种原因不起作用：

这有效，

select e.data,e.onorar,d.data,d.suma 
from contract_j e 
join rata d on e.id_cj = d.id_cj 
join persoana l on l.id_p = e.id_avocat

但这不是

select * from (
select a.*, rownum as rnum from (

select e.data,e.onorar,d.data,d.suma 
from contract_j e 
join rata d on e.id_cj = d.id_cj 
join persoana l on l.id_p = e.id_avocat) a 

where rownum <= :maxrow) 
where rnum >= :minrow

它表示第2行含糊不清的列

为什么呢？我无法理解......

Answer 1

data列在SELECT中2次引用内部查询中的不同表，而在外部查询中它变得模棱两可！因此，只需在内部查询中添加合适的别名即为唯一

select * from (
select a.*, rownum as rnum from (

select e.data as e_data,e.onorar,d.data as d_data,d.suma 
from contract_j e 
join rata d on e.id_cj = d.id_cj 
join persoana l on l.id_p = e.id_avocat) a 

where rownum <= :maxrow) 
where rnum >= :minrow