您可以使用函数 concat_ws 跳过 null 值.

You can use the function concat_ws which skips the null values.

select username,
concat_ws(','
         ,case when admin_for_blog is not null then 'ADMIN' end
         ,case when editor_for_blog is not null then 'EDITOR' end
         ,case when author_for_blog is not null then 'AUTHOR' end
         )
from account