Select or create new

There are some contexts where this is possible and makes sense, but there are more that don’t.

If you have a hard-coded choices list, or if the select list is being built from a foreign key, doing it this way is going to be problematic. (For some thoughts on this, see Should I be using a foreign key?)

For those cases where it does make sense, see:
Muttiple datatime fields sort by most recent - #20 by KenWhitesell.