1) This is using your home directory as the database store which is a network filesystem. Due to this, you should *NOT* use this with large or important databases!
2) Make sure you *always* issue the shutdown command when you are finished.
If you need to use this with large or persistent databases then you'll have to make other arrangements. Also, there are various information sources on mysql on the web - see http://www.mysql.com/ to start with.
You just need to set it up so as it uses a user-owned db directory and run it with a socket file (or user port). Here are some general instructions (replace <user> with your username):
# set things up
mkdir -p /home/<user>/mysql/data
# start the daemon (in background)
/usr/libexec/mysqld --skip-networking \
# set root password (always a good idea, unless directory protected)
mysqladmin --socket=/home/<user>/mysql/mysqld.sock -u root password
# connect and do something mysql --socket=/home/<user>/mysql/mysqld.sock -u root
# stop the daemon
mysqladmin --socket=/home/<user>/mysql/mysqld.sock -u root shutdown