If you have an actual business-logic requirement to restrict a field to no more than N characters, then by all means use varchar(N); that's what it's for. But I agree with what I think Josh meant: there is very seldom any non-broken reason to have a hard upper limit on string lengths. If you think you need varchar(N) you should stop and ask why exactly. If you cannot give a specific, coherent reason why the particular value of N that you're using is the One True Length for the field, then you really need to think twice.
One nice reason to have like VARCHAR(4096) or whatever is that if there is a bug in your website and you forget to length check some user input, it stops them from screwing you by uploading megs and megs of data into a 'firstname' field, say.
Chris
---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
