Is there a way to know if It's a number?

[Jochen Haeberle]

Hi,

is there a way to check if a value is a number?
Something like SELECT isNumber(string)?

I am having problems at my website the people are sometimes entering 
strings into fields that will be calculated with later on in MySQL 
(currency units). I know there are other solutions to checking if a 
value is a number (including JavaScript), but I do not want to use 
another solution just for this.

Thanks in advance

Jochen

...and I did look into the maual first...