[SQL] How I can check a substring is a valid number in postgresql ?

[Anoop G]

Dear All,

    How I can check a substring is a valid number in postgresql ?


example:

I have a query

select max(substring(code,2,length(code))::INT) from emp where
substring(code,0,2) = 'A';



code
========
A0001
A0002
ABC005
S0002

This query fails because of ABC002, how I can avoid this error , if there is
a any way to check substring(code,1,length(code))  is a number ,then i can
correct the query by put it in where condition.

I want to get the result as 2(ie want to avoid checking ABC005

is there is any built in function to check the substring is a number in
postgresql?

Iam using  postgres 8.1.8

 pls help me


thanks in advance:

Anoop