Currently I am using DECODE functionality like this.
USERAL CHAR "DECODE (RTRIM(:USERAL),'', NULL,'<>', NULL,NULL,NULL, RTRIM(:USERAL) )"
In this case i have identified only '' and '<>' as the special characters which when occurs the field will be decoded as NULL.
But what i need is "USERAL should accept only numbers, so any other special characters should be DECODED as NULL." I don't know the list of special characters that would come in the way. It seems like we are encountering special characters every time. So, i had to change the code every time. So, i need a functionality where i would check like if it isn't a number then that should be decoded as null. Please suggest.