将字符串转换为int，并在Where子句中使用

Question

如何转换字符串字段并将其用于Where clause.Am获取这样的异常请帮助找到错误的东西。

select * from student 
where (cast (nvl(linerevnum,'0') as int)) = 1 

linerevnum是VARCHAR2

例外： 无效号码

Answer 1

仅是数字

select * from student 
where 
    (
    case when ISNUMERIC(linerevnum) 
    then cast (linerevnum as int) 
    else null 
    end ) = 1 

或简单，当比较：

select * from student 
linerevnum = '1'