I fairly new to this. Basically I have about 25,000 users in a list. And as the first step I want them to vadliate their Id whcih contains a letter followed by 6 digits, as in "a123456". As there are 25,000 of these I could either add these as a list to a rle of allowed entries or specify a grammar rule. If either way better?
I understand I can right a grammar rule but them seem confusing.