Arduino Yun mysql client database

Hello guys, I would like to know to make a mysql database where i want client to log in and sign up on the arduino serial monitor how can i do this
I've got an arduino yun with monted sd card

(sorry for my bad english)

Are you trying to:
-Host the database on the Yun (possible, though complex queries are slow)?
-Connect to an external database and send commands such as create user (also possible)?
Both?