Go to MySQL and execute the query,
>>
mysql > select * from wp_options where option_name = 'template' or option_name = 'stylesheet' or option_name = 'current_theme';
Here, the o/p will be in the form
+———–+—————+————–+———-+
| option_id | option_name | option_value | autoload |
+———–+—————+————–+———-+
| 149 | current_theme | themename | yes |
| 45 | stylesheet | themename | yes |
| 44 | template | themename | yes |
+———–+—————+————–+———-+
To change , ie changing current theme 'themename' to 'newtheme' execute
update wp_options set option_value = 'new theme' where option_name = 'template';
update wp_options set option_value = 'new theme' where option_name = 'stylesheet';
update wp_options set option_value = 'new theme' where option_name = 'current_theme';
>>
mysql > select * from wp_options where option_name = 'template' or option_name = 'stylesheet' or option_name = 'current_theme';
Here, the o/p will be in the form
+———–+—————+————–+———-+
| option_id | option_name | option_value | autoload |
+———–+—————+————–+———-+
| 149 | current_theme | themename | yes |
| 45 | stylesheet | themename | yes |
| 44 | template | themename | yes |
+———–+—————+————–+———-+
To change , ie changing current theme 'themename' to 'newtheme' execute
update wp_options set option_value = 'new theme' where option_name = 'template';
update wp_options set option_value = 'new theme' where option_name = 'stylesheet';
update wp_options set option_value = 'new theme' where option_name = 'current_theme';