Moving WordPress site from one domain to another

Hello,

I was helping a friend design his website. When we first launched it, he had purchased the hosting, but wasn’t sure what he wanted his domain to be. So I went a head and created a subdomain on my site and change the a record and such, so we could design his site.

He has since purchased his domain. If I change the A Record and Cname to point to his domain will it delete everything we’ve done in WordPress?