Merging user information in databases.

[Chrism13]

First of all, I wish everyone good days and blessed RAMADANs. I have a website with subdomains. Let me explain it like this: Www.Site.comSub1.site.comSub2.site.comSub3.site.com, and so on. I am thinking of adding news, forums, and other scripts to these subdomains, if God wills. Can I merge the databases of all users on these subdomains with the main site, or how can I do that? In other words, when a user signs up on the main site, all scripts on the subdomains should also use this data. Secondly, I want to redirect these subdomains to a separate domain. In other words, I want to publish the same site as both a subdomain and a separate domain. Like this: Sub1.site.com/samplepageWww.anothersite.com/samplepage. The content will be the same, only copied from the subdomain to the other site, not just redirected. It may sound a bit complicated, but God willing, I have been able to explain. Thank you in advance, may God be with you, and have a blessed RAMADAN...