ruby on rails install mysql2 but not show

I know may be this is a popular problem but i try many solutions and not get to finish

I try to install mysql in rails with

gem install mysql2

And I get the result

Building native extensions.  This could take a while...
Successfully installed mysql2-0.3.18
1 gem installed

But when i try to execute the command

bundle show mysql2

I get

Could not find gem 'mysql2'.

All these command execute in my application root directory

What is the problem ?