select s_id, s_name from student where s_id notin ( select s_id from score a, course b, teacher c where a.c_id = b.c_id and b.t_id = c.t_id and c.t_name ='张三' )
SELECT b.book_main_id, b.name, b.author, b.last_update_time, b.last_update_content from (select author, max(last_update_time) as last_update_time from book_main where author in ('$authors_str') groupby author) as a, book_main as b where a.author=b.author and a.last_update_time=b.last_update_time";