SQL练习

创建表

#教师表
CREATE TABLE teacher(
    tno INT NOT NULL PRIMARY KEY,
    tname VARCHAR(20) NOT NULL
);
INSERT INTO teacher(tno,tname)VALUES(1,'张老师');
INSERT INTO teacher(tno,tname)VALUES(2,'王老师');
INSERT INTO teacher(tno,tname)VALUES(3,'李老师');
INSERT INTO teacher(tno,tname)VALUES(4,'赵老师');
INSERT INTO teacher(tno,tname)VALUES(5,'刘老师');
INSERT INTO teacher(tno,tname)VALUES(6,'向老师');
INSERT INTO teacher(tno,tname)VALUES(7,'李文静');
INSERT INTO teacher(tno,tname)VALUES(8,'叶平');

#学生表
CREATE TABLE student(
    sno int NOT NULL PRIMARY KEY,
    sname varchar(20) NOT NULL,
    sage datetime NOT NULL,
    ssex char(2) NOT NULL
);
INSERT INTO student(sno,sname,sage,ssex) VALUES(1,'张三','1980-1-23','男');
INSERT INTO student(sno,sname,sage,ssex) VALUES(2,'李四','1982-12-12','男');
INSERT INTO student(sno,sname,sage,ssex) VALUES(3,'张飒','1981-9-9','男');
INSERT INTO student(sno,sname,sage,ssex) VALUES(4,'莉莉','1983-3-23','女');
INSERT INTO student(sno,sname,sage,ssex) VALUES(5,'王弼','1982-6-21','男');
INSERT INTO student(sno,sname,sage,ssex) VALUES(6,'王丽','1984-10-10','女');
INSERT INTO student(sno,sname,sage,ssex) VALUES(7,'刘香','1980-12-22','女');

-- 课程表
CREATE TABLE course(
	--课程编号
    cno int NOT NULL PRIMARY KEY,
	--课程名称
    cname nvarchar(20) NOT NULL,
	--老师编号
    tno int NOT NULL
);
-- 添加外键
ALTER TABLE course
ADD CONSTRAINT fk_course_teacher
FOREIGN KEY (tno) REFERENCES teacher (tno);
insert into course(cno,cname,tno) values(1,'企业管理',3);
insert into course(cno,cname,tno) values(2,'马克思',1);
insert into course(cno,cname,tno) values(3,'UML',2);
insert into course(cno,cname,tno) values(4,'数据库',5);
insert into course(cno,cname,tno) values(5,'物理',8);

-- 创建成绩表
CREATE TABLE sc(
    --学生学号
    sno int NOT NULL,
	--课程编号
    cno int NOT NULL,
	--成绩
    score int NOT NULL
);

ALTER TABLE sc
ADD CONSTRAINT fk_sc_course
FOREIGN KEY (cno) REFERENCES course (cno);

ALTER TABLE sc
ADD CONSTRAINT fk_sc_student
FOREIGN KEY (sno) REFERENCES student (sno);

INSERT INTO sc(sno,cno,score)VALUES(1,1,80);
INSERT INTO sc(sno,cno,score)VALUES(1,2,86);
INSERT INTO sc(sno,cno,score)VALUES(1,3,83);
INSERT INTO sc(sno,cno,score)VALUES(1,4,89);

INSERT INTO sc(sno,cno,score)VALUES(2,1,50);
INSERT INTO sc(sno,cno,score)VALUES(2,2,36);
INSERT INTO sc(sno,cno,score)VALUES(2,3,43);
INSERT INTO sc(sno,cno,score)VALUES(2,4,59);

INSERT INTO sc(sno,cno,score)VALUES(3,1,50);
INSERT INTO sc(sno,cno,score)VALUES(3,2,96);
INSERT INTO sc(sno,cno,score)VALUES(3,3,73);
INSERT INTO sc(sno,cno,score)VALUES(3,4,69);

INSERT INTO sc(sno,cno,score)VALUES(4,1,90);
INSERT INTO sc(sno,cno,score)VALUES(4,2,36);
INSERT INTO sc(sno,cno,score)VALUES(4,3,88);
INSERT INTO sc(sno,cno,score)VALUES(4,4,99);

INSERT INTO sc(sno,cno,score)VALUES(5,1,90);
INSERT INTO sc(sno,cno,score)VALUES(5,2,96);
INSERT INTO sc(sno,cno,score)VALUES(5,3,98);
INSERT INTO sc(sno,cno,score)VALUES(5,4,99);

INSERT INTO sc(sno,cno,score)VALUES(6,1,70);
INSERT INTO sc(sno,cno,score)VALUES(6,2,66);
INSERT INTO sc(sno,cno,score)VALUES(6,3,58);
INSERT INTO sc(sno,cno,score)VALUES(6,4,79);

INSERT INTO sc(sno,cno,score)VALUES(7,1,80);
INSERT INTO sc(sno,cno,score)VALUES(7,2,76);
INSERT INTO sc(sno,cno,score)VALUES(7,3,68);
INSERT INTO sc(sno,cno,score)VALUES(7,4,59);
INSERT INTO sc(sno,cno,score)VALUES(7,5,89);

1、查询课程1的成绩 比 课程2的成绩 高 的所有学生的学号；

SELECT sno FROM
(SELECT sno,score FROM sc WHERE cno=1) AS a,
(SELECT sno,score FROM sc WHERE cno=2) AS b
WHERE 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 sno,AVG(score) AS sscore FROM sc GROUP BY sno HAVING AVG(score) >60;

3、查询所有同学的学号、姓名、选课数、总成绩；

SELECT
	a.sno AS '学号',
	b.sname AS '姓名',
	count(a.cno) AS '选课数',
	SUM(a.score) AS '总成绩'
FROM
	sc a,
	student b
WHERE
	a.sno = b.sno
GROUP BY a.sno,b.sname;

4、查询姓“李”的老师的个数；

SELECT COUNT(DISTINCT(tname)) FROM teacher WHERE tname LIKE '李%';

5、查询没学过“叶平”老师课的同学的学号、姓名；

SELECT student.sno,student.sname FROM student
WHERE sno NOT IN (SELECT DISTINCT(sc.sno) FROM sc,course,teacher
WHERE sc.cno=course.cno AND teacher.tno=course.tno AND teacher.tname='叶平');