查詢有關數據庫管理系統

Question

我想寫這些查詢

• 顯示誰從來沒有借出的詩集學生的名字。
• 顯示借出5本以上書籍的學生的姓名。
• 顯示學生姓名，書名，發行日期以及所有預訂書籍的作者姓名。

查詢我寫了那麼遠是不工作的第一項任務

SELECT 
    name  
FROM 
    students 
INNER JOIN issued ON students.rollno = issued.rollno 
GROUP BY 
    issued.rollno 
HAVING 
    COUNT(issued.rollno)> 2 

Answer 1

給這些查詢試試

select s.name from students s 
left join issued i on (s.rollno = i.rollno) 
left join bookcopy bc on (i.copyid = bc.copyid) 
left join books b on (bc.bookid = b.bookid) 
left join category c on (b.catid = c.catid and c.catname = 'Poetry') 
where c.catid is null 

select s.name, count(*) as from students s 
left join issued i on (s.rollno = i.rollno) 
group by s.name 
having count(*) > 5 

select s.name, b.title, a.authorname, i.issuedate from students s 
left join issued i on (s.rollno = i.rollno) 
left join bookcopy bc on (i.copyid = bc.copyid) 
left join books b on (bc.bookid = b.bookid) 
left join author a on (b.authorid = a.authorid);