How can I determine if a string is numeric in SQL?

Question

In a SQL query on Oracle 10g, I need to determine whether a string is numeric or not. How can I do this?

Answer 1

I found that the solution

LENGTH(TRIM(TRANSLATE(string1, ' +-.0123456789', ' '))) is null

allows embedded blanks ... it accepts "123 45 6789" which for my purpose is not a number.

Another level of trim/translate corrects this. The following will detect a string field containing consecutive digits with leading or trailing blanks such that to_number(trim(string1)) will not fail

LENGTH(TRIM(TRANSLATE(translate(trim(string1),' ','X'), '0123456789', ' '))) is null