MySQL（學生表、教師表、課程表、成績表）多表查詢

1、表架構

student(sid,sname,sage,ssex) 學生表 
course(cid,cname,tid) 課程表 
sC(sid,cid,score) 成績表 
teacher(tid,tname) 教師表

2、建表sql語句

 

CREATE TABLE student 
  ( 
     sid INT PRIMARY KEY NOT NULL,
     sname VARCHAR(30), 
     sage INT, 
     ssex VARCHAR(8) 
  )  
 
CREATE TABLE course 
  ( 
     cid INT PRIMARY KEY NOT NULL, 
     cname VARCHAR(30), 
     tid INT 
  ) 
 
CREATE TABLE sc 
  ( 
     sid INT NOT NULL, 
     cid INT NOT NULL, 
     score INT 
  )  
 
CREATE TABLE teacher 
  ( 
     tid INT PRIMARY KEY NOT NULL, 
     tname VARCHAR(30) 
  )

 

3、問題：
（1）查詢“30001”課程的所有學生的學號與分數； 

SELECT sid,score FROM sc WHERE cid="30001"

 

（2）查詢“001”課程比“002”課程成績高的所有學生的學號與分數；

SELECT a.sid,a.score FROM (SELECT sid,score FROM sc WHERE cid="30001") a,

      (SELECT sid,score FROM sc WHERE cid="30002") b

     WHERE a.score>b.score AND a.sid=b.sid

 

（3）查詢平均成績大於60分的同學的學號和平均成績；

SELECT sid,AVG(score)

FROM sc

GROUP BY sid HAVING AVG(score)>60

 

（4）查詢所有同學的學號、姓名、選課數、總成績

SELECT s.sid AS "學號", s.sname AS "姓名", COUNT(sc.cid) AS "課程數目", SUM(sc.score) AS "總分數"

FROM student s, sc sc

WHERE s.sid=sc.sid

GROUP BY s.sid

 

（5）查詢姓“李”的老師的個數；

select count(distinct(Tname))

  from teacher

  where tname like '李%';

 

（6）查詢學過“張三”老師課的同學的學號、姓名

SELECT s.sid AS "學號", s.sname AS "姓名"

FROM student s, sc sc, course c, teacher t

WHERE s.sid=sc.sid AND c.cid=sc.cid AND t.tid=c.tid AND t.tname="張三"

（7）查詢沒有學過“張三”老師課的同學的學號、姓名

SELECT s.sid, s.sname

FROM student s

WHERE s.sid NOT IN (

SELECT s.sid

FROM student s, sc sc, course c, teacher t

WHERE s.sid=sc.sid AND c.cid=sc.cid AND t.tid=c.tid AND t.tname="張三"

)

（8）查詢學過“30001”並且也學過編號“30002”課程的同學的學號、姓名 

SELECT s.sid, s.sname

FROM student s, sc sc

WHERE s.sid=sc.sid AND sc.cid="30001" AND EXISTS(

     SELECT * FROM sc AS sc2 WHERE sc2.sid=sc.sid AND sc2.cid="30002"

)

（9）查詢學過“葉平”老師所教的所有課的同學的學號、姓名；

SELECT sid, sname

FROM student

WHERE sid IN (

SELECT sc.sid

FROM sc sc, course c, teacher t

WHERE sc.cid=c.cid AND c.tid=t.tid AND t.tname="張二"

)

（10）查詢所有課程成績小於60分的同學的學號、姓名

SELECT sid, sname FROM student

WHERE sid NOT IN (

SELECT DISTINCT(sc.sid) FROM student s, sc sc

WHERE sc.sid=s.sid AND sc.score>60)

 

（11）查詢沒有學全所有課的同學的學號、姓名；

SELECT sid, sname FROM student 

WHERE sid NOT IN(

SELECT s.sid FROM student s, sc sc

WHERE sc.sid=s.sid

GROUP BY s.sid

HAVING COUNT(sc.cid)=(

SELECT COUNT(cid) FROM course))

（12）查詢各科成績最高和最低的分：以如下形式顯示：課程ID，最高分，最低分

SELECT cid AS "課程ID", MAX(score) AS "最高分", MIN(score) AS "最低分"
FROM sc
GROUP BY cid

（13）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

(方式一)
SELECT sc.cid AS "課程ID",c.cname AS "課程名", AVG(sc.score) AS "平均成績",
SUM(CASE WHEN sc.score > 60 THEN 1 ELSE 0 END)/COUNT(1)*100 AS "及格百分數"
FROM sc sc, course c
WHERE sc.cid=c.cid
GROUP BY sc.cid
ORDER BY AVG(sc.score) ASC,
SUM(CASE WHEN sc.score > 60 THEN 1 ELSE 0 END)/COUNT(1)*100 DESC


(方式二)
SELECT sc.cid AS "課程ID",c.cname AS "課程名", IFNULL(AVG(sc.score),0) AS "平均成績",
100*SUM(CASE WHEN IFNULL(sc.score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) AS "及格百分數"
FROM sc sc, course c
WHERE sc.cid = c.cid
GROUP BY sc.cid
ORDER BY AVG(sc.score) ASC,
100*SUM(CASE WHEN IFNULL(sc.score,0)>=60 THEN 1 ELSE 0 END)/COUNT(*) DESC

（14）查詢所有學生的所有科目的成績單（學號、姓名、語文、數學、英語、物理、平均分、總分（按照總分由高到低排序））

SELECT s.sid AS "學號", s.sname AS "姓名",
SUM(CASE c.cname WHEN "語文" THEN sc.score ELSE 0 END) AS "語文",
SUM(CASE c.cname WHEN "數學" THEN sc.score ELSE 0 END) AS "數學",
SUM(CASE c.cname WHEN "英語" THEN sc.score ELSE 0 END) AS "英語",
SUM(CASE c.cname WHEN "物理" THEN sc.score ELSE 0 END) AS "物理",
IFNULL(AVG(sc.score),0) AS "平均分",
IFNULL(SUM(sc.score),0) AS "總分"
FROM student s
LEFT OUTER JOIN sc sc ON s.sid=sc.sid
LEFT OUTER JOIN course c ON sc.cid=c.cid
GROUP BY s.sid, s.sname
ORDER BY IFNULL(SUM(sc.score),0) DESC

（15）查詢總分排名在200-300（包含200和第300）之間的學生所有成績單信息

SELECT s.sid AS "學號", s.sname AS "姓名",
SUM(CASE c.cname WHEN "語文" THEN sc.score ELSE 0 END) AS "語文",
SUM(CASE c.cname WHEN "數學" THEN sc.score ELSE 0 END) AS "數學",
SUM(CASE c.cname WHEN "英語" THEN sc.score ELSE 0 END) AS "英語",
SUM(CASE c.cname WHEN "物理" THEN sc.score ELSE 0 END) AS "物理",
IFNULL(AVG(sc.score),0) AS "平均分",
IFNULL(SUM(sc.score),0) AS "總分"
FROM student s
LEFT OUTER JOIN sc sc ON s.sid=sc.sid
LEFT OUTER JOIN course c ON sc.cid=c.cid
GROUP BY s.sid, s.sname
HAVING IFNULL(SUM(sc.score),0) BETWEEN 200 AND 300
ORDER BY IFNULL(SUM(sc.score),0) DESC

（16）查詢總分排名在前四名的學生所有成績單信息

SELECT s.sid AS "學號", s.sname AS "姓名",
SUM(CASE c.cname WHEN "語文" THEN sc.score ELSE 0 END) AS "語文",
SUM(CASE c.cname WHEN "數學" THEN sc.score ELSE 0 END) AS "數學",
SUM(CASE c.cname WHEN "英語" THEN sc.score ELSE 0 END) AS "英語",
SUM(CASE c.cname WHEN "物理" THEN sc.score ELSE 0 END) AS "物理",
IFNULL(AVG(sc.score),0) AS "平均分",
IFNULL(SUM(sc.score),0) AS "總分"
FROM student s
LEFT OUTER JOIN sc sc ON s.sid=sc.sid
LEFT OUTER JOIN course c ON sc.cid=c.cid
GROUP BY s.sid, s.sname
ORDER BY IFNULL(SUM(sc.score),0) DESC
LIMIT 0,4

（17）查詢總分排名在前二名到四名的學生所有成績單信息（limit 1,3表示從第二條數據開始，連續三條數據）

SELECT s.sid AS "學號", s.sname AS "姓名",
SUM(CASE c.cname WHEN "語文" THEN sc.score ELSE 0 END) AS "語文",
SUM(CASE c.cname WHEN "數學" THEN sc.score ELSE 0 END) AS "數學",
SUM(CASE c.cname WHEN "英語" THEN sc.score ELSE 0 END) AS "英語",
SUM(CASE c.cname WHEN "物理" THEN sc.score ELSE 0 END) AS "物理",
IFNULL(AVG(sc.score),0) AS "平均分",
IFNULL(SUM(sc.score),0) AS "總分"
FROM student s
LEFT OUTER JOIN sc sc ON s.sid=sc.sid
LEFT OUTER JOIN course c ON sc.cid=c.cid
GROUP BY s.sid, s.sname
ORDER BY IFNULL(SUM(sc.score),0) DESC
LIMIT 1,3

（18）查詢學生平均成績及其名次

(非本人)
SELECT 1+(SELECT COUNT( distinct 平均成績)
FROM (
SELECT sid,AVG(score) AS 平均成績
FROM sc
GROUP BY sid ) AS T1
WHERE 平均成績 > T2.平均成績) as 名次, S# as 學生學號,平均成績
FROM (SELECT sid,AVG(score) 平均成績
FROM sc GROUP BY sid ) AS T2
ORDER BY 平均成績 desc

原文鏈接：https://blog.csdn.net/PGY0000/article/details/83002561