how do i delete a many-to-one relationship?

Because every save is associated with:

• connecting (if is not connected)
• sending query to server
• parsing query
• inserting row
• inserting indexes
• closing (options – you will keep connection)

Generally if you use statement with many insert at the same time you should use INSERT with many VALUES. This is faster, sometimes many time faster, because you sending data once, you parse query once, you indexing once etc… so second approach is better

But you can improve speed of first approach by using transactions