Configure 2 sites to access one user table

[mark1491]

I have two 4images sites on the same server with different domains.  I would like both sites to access the same user database table.  I saw this a while ago on how it might be done, but I can't find it anymore when I search. 

I thought that it might just be done with an mysql command, which will point one table to the other.

Thanks in advance,
Mark