To change the current theme to twentyfourteen default theme

>> mysql

>> use database_name;

To see current theme

>> select * from wp_options where option_name = ‘template’ or option_name = ‘stylesheet’ or option_name = ‘current_theme’;

>> update wp_options set option_value = ‘twentyfourteen’ where option_name = ‘template’;
>> update wp_options set option_value = ‘twentyfourteen’ where option_name = ‘stylesheet’;
>> update wp_options set option_value = ‘twentyfourteen’ where option_name = ‘current_theme’;

Thats it!

• MySQL
• wordpress