I'm looking for some syntax help to remove characters in a string. I have a field called zipcode, which has some different formats in it. I'd like to remove any characters after the first 5.

for example: 12345-1234
would return: 12345

I've looked at TRIM() and RTRIM(), but I don't see how to do the above when I don't know what the sting contains, other than it's length?