If you have more then one mysql installed on your computer and in your path is not proper MYSQL, you should run
?/Applications/MAMP/Library/bin/mysql --host=localhost -uroot -proot
to start MAMP mysql, and to check if the one you want to use is right, run show databases;
Kind of a newbee thing, but could help for Frontenders and people not so good with AMP stacks.