Drop a colomn form a table
ALTER TABLE tb_name DROP COLUMN column_name ;
Give a user all permission to a table
GRANT ALL PRIVILEGES ON dbTest.* To 'user'@'hostname' IDENTIFIED BY 'password';
Change databse charset to utf-8：
ALTER DATABASE databasename CHARACTER SET utf8 COLLATE utf8_unicode_ci;
ALTER TABLE tablename CONVERT TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;
Install mysql in rails
sudo apt-get install mysql-server-xx
sudo apt-get install libmysqlclient-dev
gem install mysql2