First of all I don't recommend you doing that. Importantly if you are planning to put Google adsense in there. Google will track you down and remove you from their program. But if you are doing it for fun or other purposes. Here is what you can do.

You can connect database by configuring wpconfig.php file where you will provide database name, password and table info. So pretty much you can use sampe wpconfig.php file in both blog folder.

I hope it helps.