You can not really learn MySQL, as it is an program. You can either learn how to administrate an MySQL-Server or you learn the language, used to "talk" to the MySQL Server to manipulate data. This language is called SQL and is not restricted to MySQL (some functions are always dependent on the server, but the main language is universal).
Do you have any experience in any programming language? Learning SQL without an programming language doesn't make too much sense.
glitzi