Fatal error: Call to a member function num_rows() on a non-object in

Problem:

While working with CodeIgniter you can get this "Fatal error: Call to a member function num_rows() on a non-object in...." error. You can also surprise that every thing is okay and every thing is okay in your sql.

Solution:

Some time you used different my sql Database name in local and production server, and you have mentioned wrong database name in your config.php file, So just verify the Database name and this error will gone.