題目(詳解 11-20):
11.查詢至少有一門課與學號爲“01”的同學所學相同的同學的學號和姓名;
SELECT s.sid,s.sname
FROM student s,sc
WHERE s.sid=sc.sid
AND sc.cid IN (SELECT cid FROM sc WHERE sid=01)
AND sc.sid<>01
GROUP BY s.sid;
12.查詢和"01"號的同學學習的課程完全相同的其他同學的學號和姓名
SELECT cid FROM sc WHERE sid=01;
SELECT s.sid,s.sname FROM student s,sc
WHERE s.sid=sc.sid
AND s.sid<>01
GROUP BY sc.sid
HAVING COUNT(*)=
(SELECT COUNT(*) FROM sc WHERE sid=01 GROUP BY sid)
13.把“SC”表中“張三”老師教的課的成績都更改爲此課程的平均成績;
update SC,(
SELECT t.tid,avg(score) as ascore
from Course as c,SC as sc,Teacher as t
WHERE t.tname='張三'
AND c.tid=t.tid AND c.cid=sc.cid) a
set score=a.ascore;
14、查詢沒學過"張三"老師講授的任一門課程的學生姓名(同5)
SELECT * FROM Student WHERE sid in(
SELECT sid FROM SC WHERE cid NOT in(
SELECT cid
FROM Teacher,Course WHERE Teacher.tname='張三' AND Teacher.tid=Course.tid
)
)
15、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 s.sid,s.sname,AVG(sc.score)
FROM student s,sc
WHERE s.sid=sc.sid
AND sc.score<60
GROUP BY sc.sid
HAVING COUNT(cid)>=2;
16、檢索"01"課程分數小於60,按分數降序排列的學生信息
SELECT s.*,sc.score
FROM student s,sc
WHERE s.sid=sc.sid
AND sc.cid=01 AND sc.score<60
ORDER BY sc.score DESC;
SELECT Student.*,SC.score FROM Student,SC WHERE EXISTS (
SELECT sid,score FROM SC WHERE cid=01 AND score<60 AND sid=Student.sid
) AND Student.sid=SC.sid AND SC.cid=01 ORDER BY SC.score DESC;
17、按平均成績從高到低顯示所有學生的所有課程的成績以及平均成績
SELECT s.*,
SUM(CASE WHEN sc.cid='01' THEN sc.score ELSE 0 END) s01,
SUM(CASE WHEN sc.cid='02' THEN sc.score ELSE 0 END) s02,
SUM(CASE WHEN sc.cid='03' THEN sc.score ELSE 0 END) s03,
AVG(CASE WHEN sc.score IS NULL THEN 0 ELSE sc.score END) avs
FROM student s LEFT JOIN sc
ON s.sid=sc.sid
GROUP BY 1,2,3,4
#GROUP BY s.sid
ORDER BY avs DESC;
18.查詢各科成績最高分、最低分和平均分:以如下形式顯示:課程ID,課程name,最高分,最低分,平均分,及格率,中等率,優良率,優秀率
SELECT c.cid,c.cname,
MAX(sc.score),MIN(sc.score),AVG(sc.score),
SUM(CASE WHEN sc.score >= 60 THEN 1 ELSE 0 END)/COUNT(1) s1,
SUM(CASE WHEN sc.score >= 70 AND sc.score < 80 THEN 1 ELSE 0 END)/COUNT(1) s2,
SUM(CASE WHEN sc.score >= 80 AND sc.score < 90 THEN 1 ELSE 0 END)/COUNT(1) s3,
SUM(CASE WHEN sc.score >= 90 THEN 1 ELSE 0 END)/COUNT(1) s4
FROM course c,sc
WHERE c.cid=sc.cid
GROUP BY sc.cid
19.按各科平均成績從低到高和及格率的百分數從高到低順序
SELECT cid,avs,CONCAT(rate,'%') 及格率
FROM(
SELECT sc0.cid,
AVG(sc0.score) avs,
CAST((
SELECT COUNT(1) FROM SC WHERE cid=sc0.cid AND score>=60
)*1.0/(
SELECT COUNT(1) FROM SC WHERE cid=sc0.cid
)*100 AS DECIMAL(10,2)) rate
FROM sc sc0
GROUP BY sc0.cid
ORDER BY avs,rate DESC)a;
20、查詢學生的總成績並進行排名
SELECT s.sid,s.sname,
SUM(CASE WHEN sc.score IS NULL THEN 0 ELSE sc.score END) ss
FROM student s LEFT JOIN sc
ON s.sid=sc.sid
GROUP BY sc.sid
ORDER BY ss DESC;