例如：
select (a+b) as c,(d*c) as e ,(f*c) as n from table
我想这样写，但是报错 没有c这个字段，请问大神们怎么解决呢
select c,(d*c) as e ,(f*c) as n from (
select (a+b) as c,d ,f from table) as ll
这个的确不行，必须在外面嵌套
查出来的字段是平级的，不存在先后关系
select (a+b) as c,(d*(a+b)) as e ,(f*(a+b)) as n from table