Question

can i create as many as 500000000 databases in Mysql??

If yes, is it efficient??

here, each database holds user data with 6 tables in it containing user info in it..

please explain me the pros and cons of this idea with respect to performance and implementation..

Answer 1

Please Don’t!

Whatever you’re thinking, whatever the reason. There is absolutely no way that creating that many databases is a good idea.

If you’re looking for storing data per user, or for every X. Then please take a look again at what a relational database is “A relational database matches data by using common characteristics found within the data set.”

Let’s say you’re createing an image service and want each user to have their own images. One way is to give each user their own database. This is wrong, because the data for each user contains the same characteristics, the only thing that is different is the relation (user A has picture A, user B has picture B), (1 user has 0…* pictures, and 1 picture belongs to 1 user). So instead of creating that many databases, you create a user table, and relate that to a picture table, this way you’ve efficiently used a database.

To answer your more direct question. Create a table with 50.000 entries is surely more efficient then creating 50.000 databases.

Edit a related answer on mysql.com: http://forums.mysql.com/read.php?20,74692,74705#msg-74705