准备工作
1、 创建数据表
CREATE TABLE student(
sno VARCHAR(10) PRIMARY KEY,
sname VARCHAR(20),
sage VARCHAR(2),
ssex VARCHAR(5)
);
CREATE TABLE teacher(
tno VARCHAR(10) PRIMARY KEY,
tname VARCHAR(20)
);
CREATE TABLE course(
cno VARCHAR(10),
cname VARCHAR(20),
tno VARCHAR(20),
CONSTRAINT pk_course PRIMARY KEY (cno,tno)
);
CREATE TABLE sc(
sno VARCHAR(10),
cno VARCHAR(10),
score NUMERIC(4,2),
CONSTRAINT pk_sc PRIMARY KEY (sno,cno)
);
2、 插入数据
/*******初始化学生表的数据******/
insert into student values ('s001','张三',23,'男');
insert into student values ('s002','李四',23,'男');
insert into student values ('s003','吴鹏',25,'男');
insert into student values ('s004','琴沁',20,'女');
insert into student values ('s005','王丽',20,'女');
insert into student values ('s006','李波',21,'男');
insert into student values ('s007','刘玉',21,'男');
insert into student values ('s008','萧蓉',21,'女');
insert into student values ('s009','陈萧晓',23,'女');
insert into student values ('s010','陈美',22,'女');
commit;
/******************初始化教师表***********************/
insert into teacher values ('t001', '刘阳');
insert into teacher values ('t002', '谌燕');
insert into teacher values ('t003', '胡明星');
commit;
/***************初始化课程表****************************/
insert into course values ('c001','J2SE','t002');
insert into course values ('c002','Java Web','t002');
insert into course values ('c003','SSH','t001');
insert into course values ('c004','Oracle','t001');
insert into course values ('c005','SQL SERVER 2005','t003');
insert into course values ('c006','C#','t003');
insert into course values ('c007','JavaScript','t002');
insert into course values ('c008','DIV+CSS','t001');
insert into course values ('c009','PHP','t003');
insert into course values ('c010','EJB3.0','t002');
commit;
/***************初始化成绩表***********************/
insert into sc values ('s001','c001',78.9);
insert into sc values ('s002','c001',80.9);
insert into sc values ('s003','c001',81.9);
insert into sc values ('s004','c001',60.9);
insert into sc values ('s001','c002',82.9);
insert into sc values ('s002','c002',72.9);
insert into sc values ('s003','c002',81.9);
insert into sc values ('s001','c003','59');
commit;
结果显示：
-
学生表
-
教师表
-
课程表
-
分数表
案例测试
1、查询“c001”课程比“c002”课程成绩高的所有学生的学号；
SELECT a.* ,b.score FROM
(SELECT * FROM sc a WHERE a.`cno`='c001') a,
(SELECT * FROM sc b WHERE b.`cno`='c002') b
WHERE a.sno = b.sno AND a.score>b.score
2、查询平均成绩大于60 分的同学的学号和平均成绩；
SELECT sc.`sno`,AVG(sc.`score`)
FROM sc
GROUP BY sno HAVING AVG(sc.`score`)>60
3、查询所有同学的学号、姓名、选课数、总成绩；
SELECT b.*,a.`sname`
FROM student a,
(SELECT sc.`sno`,COUNT(sc.`cno`),SUM(sc.`score`) FROM sc GROUP BY sc.`sno`) b
WHERE a.`sno`= b.sno
或者利用内联
SELECT a.*,COUNT(b.`cno`),SUM(b.`score`) FROM student a
INNER JOIN sc b ON a.`sno`=b.`sno`
GROUP BY b.`sno`
4、查询姓“刘”的老师的个数；
SELECT COUNT(*) FROM teacher t WHERE t.`tname` LIKE '刘%'
5、查询没学过“谌燕”老师课的同学的学号、姓名；
SELECT st.`sno`,st.`sname` FROM student st
WHERE st.`sno` NOT IN
(
SELECT DISTINCT a.sno
FROM sc a,
(SELECT cs.`cno`,cs.`cname` FROM course cs WHERE cs.`tno`=(SELECT b.`tno` FROM teacher b WHERE b.`tname`='谌燕')) b
WHERE a.`cno`=b.cno
)
6、查询学过“c001”并且也学过编号“c002”课程的同学的学号、姓名；
- 先找课程id与sid,然后再内联student名单，找到具体名字。
- 代码如下:
SELECT * FROM sc a JOIN sc b ON a.`sno` =b.`sno` JOIN student stu ON a.`sno`=stu.`sno` WHERE a.cno='c001' AND b.cno='c002'
7、查询学过“谌燕”老师所教的所有课的同学的学号、姓名；
SELECT d.`sno`,d.`sname`,b.`cname`,c.`tname` FROM sc a
LEFT JOIN course b ON a.`cno`=b.`cno`
LEFT JOIN teacher c ON b.`tno`=c.`tno`
LEFT JOIN student d ON a.`sno` = d.`sno`
WHERE c.`tname`='谌燕'
8、查询课程编号“c002”的成绩比课程编号“c001”课程低的所有同学的学号、姓名；
SELECT c.`sno`,c.`sname`,a.`score`,b.`score` FROM sc a
LEFT JOIN sc b ON a.`sno`=b.`sno`
LEFT JOIN student c ON a.`sno`=c.`sno`
WHERE a.`cno`='c001' AND b.`cno`='c002' AND a.`score`>b.`score`
(未完成) 9、查询所有课程成绩小于60 分的同学的学号、姓名；
SELECT a.`sname`,c.`cno`,b.`sno` FROM student a
INNER JOIN sc b ON b.`sno` = a.`sno`
LEFT JOIN course c ON c.`cno`=b.`cno`
WHERE b.`score`<60
（未完成）10、查询没有学全所有课的同学的学号、姓名；
SELECT a.`sno`,a.`sname`,COUNT(sc.`cno`) FROM student a
INNER JOIN sc ON a.`sno`=sc.`sno`
GROUP BY a.`sno` HAVING COUNT(sc.`cno`)<(SELECT COUNT(cno) FROM course)
11、查询至少有一门课与学号为“s001”的同学所学相同的同学的学号和姓名；
SELECT DISTINCT c.`sname`,c.`sno` FROM sc a
LEFT JOIN sc b ON a.`cno` = b.`cno`
LEFT JOIN student c ON a.`sno` = c.`sno`
WHERE b.`sno`='s001' AND NOT a.`sno`=b.`sno`
12、查询至少学过学号为“s001”同学所有一门课的其他同学学号和姓名；
SELECT * FROM sc
LEFT JOIN student st ON st.sno=sc.sno
WHERE sc.sno<>'s001'
AND sc.cno IN (SELECT cno FROM sc WHERE sno='s001')
13、把“SC”表中“谌燕”老师教的课的成绩都更改为此课程的平均成绩；
update sc c set score=
(
select avg(c.score) from course a,teacher b
where a.tno=b.tno and b.tname='谌燕' and a.cno=c.cno
group by c.cno
)
where cno in( select cno from course a,teacher b where a.tno=b.tno and b.tname='谌燕')