假如要查找类型是'business'的书 就这样
select title,au_lname
from authors a,titles t, titleauthor ta
where type='business' and t.title_id=ta.title_id and ta.au_id=a.au_id
select title,au_lname
from authors a,titles t, titleauthor ta
where type='business' and t.title_id=ta.title_id and ta.au_id=a.au_id
where b.title_id=c.title_id and a.au_id=c.au_id不知道要的是不是这个?