Does having many databases affect MySQL performance?

Does separating tables across multiple databases improve performance?

• If I have two tables, let's say products and orders.  And if orders is mission critical let's say, but products is not and sometimes products runs large queries, if I separate the tables into two different databases, would that make the performance more independent or would I have to put them on two entirely different mysql servers?

• Answer:

  No. Putting the two tables in different databases on the same server will gain you  absolutely no performance benefit -- presuming your server becomes disk-bound when querying the "products" table, there's no dead-simple solution to gain back performance on the orders table, save for setting up replication and running your large queries on a slave.