Deleting and creatiing root site collection during package pre deployment

Background:
In a vid course I'm taking, it is demonstrating pre-deployment commands for a solution. It is solving the problem of not being able to redeploy a list that is already there. It seems good that SharePoint doesn't let you deploy a list of the same name and I'm guessing it's because you would overwrite the existing data in the list with blank data or whatever data you deploy as part of the solution. However, in a dev environment, you will need to redeploy often and won't have any live data. So the suggestion of this course is that during pre-deployment, you wipe out the root site collection and then recreate it as the first step in the deployment, before solution retraction, add, activate....

Question:
In his example, I do not believe that he has any additional site collections under /sites or anywhere else, but in my case, I have some site collections under /sites. If I delete and create the root site collection, what happens with the other site collections? Do they disappear too? If they stay, are they considered children in some way and therefore will be orphaned or are they only related by falling within the same root url and are therefore pretty much independent except for the common resources they all share?

Thanks.