Get posts from multiple tables

Is it possible to get posts from multiple tables in the database and display in a site? For example, I have a main site called https://www.example.com and subdomains like cat1.example.com and cat2.example.com. Now, can I get posts from cat1.example.com and cat2.example.com and display them in https://www.example.com? If it can be done, can you please guide me on how to do it?

Thanks for your help and have a nice day.