I think what helped me when I had a SV was the fact that I was nauseated for 2 days off and on before I actually vomited and had diarreah.
I can also say though, that I have had SV's where I only felt nausea and had diarreah only...so it just depends on your body.
I've always figured, if you are going to vomit, you will vomit no matter what. Sometimes nausea doesn't mean nothing more than your stomach sending you signals that you ate something that didn't agree with you, and to slow down.