how to change user roles for users who doesn't have any. (about 8000 users)

Question

We have about 8000 users who doesn't have any roles. we need to change them to "contributor". How can I change them to "contributor"? Should I do on database? if so, which fields I need to update?

Thanks,

Answer 1

You can do it by executing simple SQL query:

UPDATE wp_usermeta
   SET meta_value = 'a:1:{s:11:"contributor";b:1;}' 
 WHERE meta_key = 'wp_capabilities' 
   AND meta_value = 'a:1:{s:10:"subscriber";b:1;}'

This query will updated all subscribers to be contributors.