技術標籤：Java Web技術解析MySQLMySQLSQL

#查詢姓氏是李的老師的數量

select count(*) as nameNum
from teacher
where tname like '李%';

#查詢學習過張三老師課程的學生資訊
#多表聯合查詢

select student.* from student,teacher,course,score
where 
    student.sid = score.sid 
    and course.cid=score.cid 
    and course.tid = teacher.tid 
    and tname = '張三';
 

#查詢沒有學習所有課程的同學資訊
#因為有學生什麼課都沒有選，反向思考，先查詢選了所有課的學生，再選擇這些人之外的學生.

select * from student
where student.sid not in (
  select score.sid from score
  group by score.sid
  having count(score.cid)= (select count(cid) from course)
);

#查詢至少有一門課程與學號為“01”的同學所學相同的同學的資訊

select * from student 
where student.sid in (
    select score.sid from score 
    where score.cid in(
        select score.cid from score 
        where score.sid = '01'
    )
 

#查詢沒有學過張三老師的任一門課的學生姓名
#巢狀查詢

select * from student
    where student.sid not in(
        select score.sid from score where score.cid in(
            select course.cid from course where course.tid in(
                select teacher.tid from teacher where tname = "張三"
            )
        )
    );
 

#查詢兩門及其以上不及格課程的同學的學號，姓名及其平均成績

select student.sid, student.sname,b.avgScore
from student RIGHT JOIN
(select sid, AVG(score) as avgScore from score
    where sid in (
              select sid from score 
              where score<60 
              GROUP BY sid 
              HAVING count(score)>1)
    GROUP BY sid) b on student.sid=b.sid;

#檢索" 01 "課程分數小於 60，按分數降序排列的學生資訊

select student.*, score.score from student, score
where student.sid = score.sid
and score.score < 60
and cid = "01"
ORDER BY score.score DESC;