I'm working on a ticketing system in PHP and mySQL.
I have a table `support` with `id` as my primary key and AI.

I want to add `ticket_number`, so that when a ticket is submitted each ticket is assigned a unique number. I can't use mySQL to AI a second field, right? 

If I give the first ticket a number, then write a query to lookup the last `ticket_number` in the DB, then I was thinking of doing something like:

```
$ticket = 1;
$next = $ticket+1;
echo "ticket number: #".$next;

```

would this work or is there a better way?