Mysql 基础语句练习小记

课程表的创建和数据初始化 

/*
 Navicat Premium Data Transfer

 Source Server         : SQLTEST
 Source Server Type    : MySQL
 Source Server Version : 80028
 Source Host           : localhost:3306
 Source Schema         : student

 Target Server Type    : MySQL
 Target Server Version : 80028
 File Encoding         : 65001

 Date: 21/02/2022 20:54:00
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`  (
  `cno` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `cname` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `tno` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  PRIMARY KEY (`cno`, `tno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of course
-- ----------------------------
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');

SET FOREIGN_KEY_CHECKS = 1;

学生表的创建和数据初始化

/*
 Navicat Premium Data Transfer

 Source Server         : SQLTEST
 Source Server Type    : MySQL
 Source Server Version : 80028
 Source Host           : localhost:3306
 Source Schema         : student

 Target Server Type    : MySQL
 Target Server Version : 80028
 File Encoding         : 65001

 Date: 21/02/2022 20:56:46
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `sno` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `sname` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `sage` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `ssex` varchar(5) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`sno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of student
-- ----------------------------
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');

SET FOREIGN_KEY_CHECKS = 1;

成绩表的创建和数据初始化

/*
 Navicat Premium Data Transfer

 Source Server         : SQLTEST
 Source Server Type    : MySQL
 Source Server Version : 80028
 Source Host           : localhost:3306
 Source Schema         : student

 Target Server Type    : MySQL
 Target Server Version : 80028
 File Encoding         : 65001

 Date: 21/02/2022 20:58:14
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for sc
-- ----------------------------
DROP TABLE IF EXISTS `sc`;
CREATE TABLE `sc`  (
  `sno` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `cno` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `score` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`sno`, `cno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of sc
-- ----------------------------
INSERT INTO `sc` VALUES ('s001', 'c001', '78.9');
INSERT INTO `sc` VALUES ('s001', 'c002', '82.9');
INSERT INTO `sc` VALUES ('s001', 'c003', '59');
INSERT INTO `sc` VALUES ('s002', 'c001', '80.9');
INSERT INTO `sc` VALUES ('s002', 'c002', '72.9');
INSERT INTO `sc` VALUES ('s003', 'c001', '81.9');
INSERT INTO `sc` VALUES ('s003', 'c002', '81.9');
INSERT INTO `sc` VALUES ('s004', 'c001', '60.9');

SET FOREIGN_KEY_CHECKS = 1;

教师的创建和数据初始化

/*
 Navicat Premium Data Transfer

 Source Server         : SQLTEST
 Source Server Type    : MySQL
 Source Server Version : 80028
 Source Host           : localhost:3306
 Source Schema         : student

 Target Server Type    : MySQL
 Target Server Version : 80028
 File Encoding         : 65001

 Date: 21/02/2022 20:58:53
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for teacher
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher`  (
  `tno` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `tname` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`tno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES ('t001', '刘阳');
INSERT INTO `teacher` VALUES ('t002', '谌燕');
INSERT INTO `teacher` VALUES ('t003', '胡明星');

SET FOREIGN_KEY_CHECKS = 1;

SQL语句题型和答案

-- --sql语句练习--
-- 1、查询“c001”课程比“c002”课程成绩高的所有学生的学号；
select a.* 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;
--  UNION all
 select * from sc a
 where a.cno='c001' 
 and  
 --  EXISTS 用于判断查询子句是否有记录，如果有一条或多条记录存在返回 True，否则返回 False。
 exists(select * from sc b where b.cno='c002' and a.score>b.score and a.sno = b.sno)
 
 2、查询平均成绩大于60 分的同学的学号和平均成绩；
--  HAVING 子句可以让我们筛选分组后的各组数据 用于筛选
 select sno, AVG(score) 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.*,s.sname from (select sno,sum(score),count(cno) from sc group by sno) a ,student s where a.sno=s.sno

******************************************************************

4、查询姓“刘”的老师的个数；

select count(*) from teacher where tname like '刘%';

******************************************************************

5、查询没学过“谌燕”老师课的同学的学号、姓名；

select a.sno,a.sname from student a where a.sno not in
(
 select distinct s.sno from sc s,
      (
       select c.* from course c ,
           (select tno from teacher t where tname='谌燕') t
       where c.tno=t.tno
      ) b
  where s.cno = b.cno 
)
或
select * from student st where st.sno not in
(
 select distinct sno from sc s 
 join course c on s.cno=c.cno
 join teacher t on c.tno=t.tno where tname='谌燕'
)

******************************************************************

6、查询学过“c001”并且也学过编号“c002”课程的同学的学号、姓名；

select st.* from sc a 
 join sc b on a.sno=b.sno
 join student st on st.sno=a.sno
 where a.cno='c001' and b.cno='c002' and st.sno=a.sno;

******************************************************************

7、查询学过“谌燕”老师所教的所有课的同学的学号、姓名；

select st.* from student st join sc s on st.sno=s.sno
 join course c on s.cno=c.cno
 join teacher t on c.tno=t.tno
 where t.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 * from student st
 join sc a on st.sno=a.sno
 join sc b on st.sno=b.sno
 where a.cno='c002' and b.cno='c001' and a.score < b.score
******************************************************************

9、查询所有课程成绩小于60 分的同学的学号、姓名；

select st.*,s.score from student st
 join sc s on st.sno=s.sno
 join course c on s.cno=c.cno
 where s.score <60

******************************************************************

10、查询没有学全所有课的同学的学号、姓名；

select stu.sno,stu.sname,count(sc.cno) from student stu
 left join sc on stu.sno=sc.sno
 group by stu.sno,stu.sname
 having count(sc.cno)<(select count(distinct cno)from course)

或
select * from student where sno in
(
 select sno from
        (
         select stu.sno,c.cno from student stu cross join course c minus select sno,cno from sc
        )
)

******************************************************************

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 st.* from student st,
 (select distinct a.sno from
  (select * from sc) a,
  (select * from sc where sc.sno='s001') b
  where a.cno=b.cno
 ) h
 where st.sno=h.sno and st.sno<>'s001'

******************************************************************

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')

******************************************************************

14、查询和“s001”号的同学学习的课程完全相同的其他同学学号和姓名；

select* from sc where sno<>'s001'
minus
( select* from sc minus select * from sc where sno='s001')

******************************************************************

15、删除学习“谌燕”老师课的SC 表记录；

delete from sc where sc.cno in
(
 select cno from course c
 left join teacher t on  c.tno=t.tno
 where t.tname='谌燕'
)

******************************************************************

16、向SC 表中插入一些记录，这些记录要求符合以下条件：没有上过编号“c002”课程的同学学号、“c002”号课的平均成绩；

insert into sc (sno,cno,score)
 select distinct st.sno,sc.cno,(select avg(score)from sc where cno='c002')
 from student st,sc
 where not exists
 (select * from sc where cno='c002' and sc.sno=st.sno) and sc.cno='c002';

******************************************************************

17、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分

select cno ,max(score),min(score) from sc group by cno;

******************************************************************

18、按各科平均成绩从低到高和及格率的百分数从高到低顺序

select cno,avg(score),sum(case when score>=60 then 1 else 0 end)/count(*) as 及格率
from sc group by cno
order by avg(score) , 及格率 desc

******************************************************************

19、查询不同老师所教不同课程平均分从高到低显示

select max(t.tno),max(t.tname),max(c.cno),max(c.cname),c.cno,avg(score) from sc , course c,teacher t
where sc.cno=c.cno and c.tno=t.tno
group by c.cno
order by avg(score) desc

******************************************************************

20、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]

select sc.cno,c.cname,
sum(case  when score between 85 and 100 then 1 else 0 end) AS "[100-85]",
sum(case  when score between 70 and 85 then 1 else 0 end) AS "[85-70]",
sum(case  when score between 60 and 70 then 1 else 0 end) AS "[70-60]",
sum(case  when score <60 then 1 else 0 end) AS "[<60]"
from sc, course c
where  sc.cno=c.cno
group by sc.cno ,c.cname;

******************************************************************

21、查询各科成绩前三名的记录:(不考虑成绩并列情况)

select * from
(select sno,cno,score,row_number()over(partition by cno order by score desc) rn from sc)
where rn<4

******************************************************************

22、查询每门课程被选修的学生数

select cno,count(sno)from sc group by cno;

******************************************************************

23、查询出只选修了一门课程的全部学生的学号和姓名

select sc.sno,st.sname,count(cno) from student st
left join sc
on sc.sno=st.sno
group by st.sname,sc.sno having count(cno)=1;

******************************************************************

24、查询男生、女生人数

select ssex,count(*)from student group by ssex;

******************************************************************

25、查询姓“张”的学生名单

select * from student where sname like '张%';

******************************************************************

26、查询同名同性学生名单，并统计同名人数

select sname,count(*)from student group by sname having count(*)>1;

******************************************************************

27、1981 年出生的学生名单(注：Student 表中Sage 列的类型是number)

select sno,sname,sage,ssex from student t where to_char(sysdate,'yyyy')-sage =1988

******************************************************************

28、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列

select cno,avg(score) from sc group by cno order by avg(score)asc,cno desc;

******************************************************************

29、查询平均成绩大于85 的所有学生的学号、姓名和平均成绩

select st.sno,st.sname,avg(score) from student st
left join sc on sc.sno=st.sno
group by st.sno,st.sname having avg(score)>85;

******************************************************************

30、查询课程名称为“数据库”，且分数低于60 的学生姓名和分数

select sname,score from student st,sc,course c
where st.sno=sc.sno and sc.cno=c.cno and c.cname='Oracle' and sc.score<60

******************************************************************

31、查询所有学生的选课情况；

select st.sno,st.sname,c.cname from student st,sc,course c
where sc.sno=st.sno and sc.cno=c.cno;

******************************************************************

32、查询任何一门课程成绩在70 分以上的姓名、课程名称和分数；

select st.sname,c.cname,sc.score from student st,sc,course c
where sc.sno=st.sno and sc.cno=c.cno and sc.score>70

******************************************************************

33、查询不及格的课程，并按课程号从大到小排列

select sc.sno,c.cname,sc.score from sc,course c
where sc.cno=c.cno and sc.score<60 order by sc.cno desc;

******************************************************************

34、查询课程编号为c001 且课程成绩在80 分以上的学生的学号和姓名；

select st.sno,st.sname,sc.score from sc,student st
where sc.sno=st.sno and cno='c001' and score>80;

******************************************************************

35、求选了课程的学生人数

select count(distinct sno) from sc;

******************************************************************

36、查询选修“谌燕”老师所授课程的学生中，成绩最高的学生姓名及其成绩

select st.sname,score from student st,sc ,course c,teacher t
where
st.sno=sc.sno and sc.cno=c.cno and c.tno=t.tno and t.tname='谌燕' and sc.score=
(select max(score)from sc where sc.cno=c.cno)

******************************************************************

37、查询各个课程及相应的选修人数

select cno,count(sno) from sc group by cno;

******************************************************************

38、查询不同课程成绩相同的学生的学号、课程号、学生成绩

select a.* from sc a ,sc b where a.score=b.score and a.cno<>b.cno

******************************************************************

39、查询每门功课成绩最好的前两名

select * from (
 select sno,cno,score,row_number()over(partition by cno order by score desc) my_rn from sc t
)
where my_rn<=2

******************************************************************

40、统计每门课程的学生选修人数（超过10 人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列

select cno,count(sno) from sc 
group by cno having count(sno)>10
order by count(sno) desc,cno asc;

******************************************************************

41、检索至少选修两门课程的学生学号

select sno from sc group by sno having count(cno)>1;
或
select sno from sc group by sno having count(sno)>1;

******************************************************************

42、查询全部学生都选修的课程的课程号和课程名

select distinct(c.cno),c.cname from course c ,sc where sc.cno=c.cno
或
select cno,cname from course c where c.cno in (select cno from sc group by cno)

******************************************************************

43、查询没学过“谌燕”老师讲授的任一门课程的学生姓名

select st.sname from student st
where st.sno not in
(select distinct sc.sno from sc,course c,teacher t where sc.cno=c.cno and c.tno=t.tno and t.tname='谌燕')

******************************************************************

44、查询两门以上不及格课程的同学的学号及其平均成绩

select sno,avg(score)from sc
where sno in
(
 select sno from sc where sc.score<60
 group by sno having count(sno)>1
) group by sno

******************************************************************

45、检索“c004”课程分数小于60，按分数降序排列的同学学号

select sno from sc where cno='c004' and score<90 order by score desc;

******************************************************************

46、删除“s002”同学的“c001”课程的成绩

delete from sc where sno='s002' and cno='c001';