Query Exec Gem:  This gem is used to execute SQL commands in our Rails application.  Installation:  gem install query_exec  or  add gem 'query_exec'  to your gem file.   Example of Usage:  QueryExec.run('select * from users') # gives all the users from users table  QueryExec.run('update users set name='xxx' where id=2')  # updates user with name='xxx' which is having id 2.  Using this gem we can do all the SQL operatons.