What is the best solution for 2 sites integrated to each other

I have a 2 s开发者_开发知识库ites integrated into one, wordpress is my second site which is under the subdirectory of my first site "mysite/community" I have integrated their registration and login. I am being hesitant for combining their tables into one database since they uses both of their native sessions. Do I install the database of wordpress into separate one or can I combine them? I'm confused of combining them since my first site is an ecommerce site.

What is the point of integrating them?

Do you want the users to get the impression on using only one site? If so having one login and one look and feel are the important things.

Do you want to ease administration? Then merging the databases might be helpful. But honestly when talking about two databases, I won't worry to much about it.

Update:

Speed: It depends on a lot if things if two or a single database is faster. The only way to tell is really to try it. And remember tuning is only worth the effort when performance is about to become a problem.

Reliability With a single database a db problem with one site becomes automatically a problem for both sites.

Security: This is the similar to reliability: a vulnerability in one site might punch through to the other site, which is bad if one is a ecommerce site.

Maintainability: If you only have one db you only have to upgrade one, backup one, so work effort should be reduced. But: you can't upgrade one while leaving the other alone.

Usability (for the developer): one database is easier to use when you have transactions spanning both sites. If you don't have those, it doesn't matter much.