Site5 shared hosting plan is now offering unlimited mysql database feature. Meaning that there is no limitation on how many mysql database that you can create for your website(s). On site5 $5 dollars hosting plan, you are allow to host as many websites as you prefer. As there is unlimited domain pointer features, a.k.a Unlimited Domain Hosting. You can have 500 websites setup at this site5 account, and then create few mysql database for each of individual website hosted. Its possible to do that. As long you not exceed the mysql concurrent connection limit and server usage limits 
Bottom line, the unlimited mysql database feature is a very good feature to have.
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