How to convert all tables in database to one collation?

I'm getting error:

Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation '='"

I tried changing both tables manually to utf8_general_ci,IMPLICIT but I'm still getting the error.

Is there a way to convert all tables to utf8_general_ci,IMPLICIT and be done with it?