Arnaud Lesauvage <thewild(at)freesurf(dot)fr> writes:
> I am searching for a function that would return true if a string
> is a number.
> In Access I would have written IsNumeric('mystring'), but this
> function does not exist in postgres.
Write your own using a pattern test, for instance
varchar ~ '^[0-9]+$'
See
http://www.postgresql.org/docs/8.1/static/functions-matching.html
regards, tom lane