If I sync another iphone to my iTunes will this delete my previous sync on iTunes?

I synced my phone to iTunes and now let's say I want to sync my friends iphone to the same computer. Will this delete my previous sync? I'm hoping it does because I want my previous sync deleted as I don't want others getting my stuff on their iPhones thanks heaps

It will only sync the same as your iphone if you choose to, otherwise it will set as a new iphone to itunes. You can also erase your iphone from itunes just go to preference and find where it probably says devices, and click it then press delete.