I overlooked one detail. It still works, but only if there are several records in the tblreserved already. For testing (and in the sql dumb I sent you), I just happened to have each of the event dates reserved by someone. SO, if this is a fresh database and nobody has registered, or if some dates have not been registered, they are not included as a choice for anyone to register.
I tried for several hours to alter your sql before bugging you about it again. No luck.
My thoughts were that maybe I needed to include an "if" in the sql. So, if the UserID = ParamUserID or if the UserID != ParamUserID, then do all that. Otherwise include all the dates in the tblbooths table. But I couldn't get it to work.
Also, just a small added question. In your opinion, should my tblreserved table have a unique table id? Right now I have both booth_id and UserID as primary/unique together. But adding a WA delete or update behavior might not work.?