將字符串轉換爲int，並在Where子句中使用

Question

如何轉換字符串字段並將其用於Where clause.Am獲取這樣的異常請幫助找到錯誤的東西。

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

linerevnum是VARCHAR2

例外： 無效號碼

Answer 1

僅是數字

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

或簡單，當比較：

select * from student 
linerevnum = '1'