MySQL库表操作练习

库表信息

CREATE TABLE grade (
    id INT NOT NULL,
    sex CHAR(1),
    firstname VARCHAR(20) NOT NULL,
    lastname VARCHAR(20) NOT NULL,
    english FLOAT,
    math FLOAT,
    chinese FLOAT
);

INSERT INTO grade VALUES 
(1, 'm', 'John', 'Smith', 88.0, 85.0, 82.0),
(2, 'f', 'Adam', 'Smith', 76.0, 78.0, 90.0),
(3, 'm', 'Allen', 'William', 88.0, 92.0, 95.0),
(4, 'm', 'George', 'William', 62.0, 58.0, 72.0),
(5, 'f', 'Alice', 'Davis', 89.0, 94.0, 98.0),
(6, 'm', 'Kevin', 'Miller', 77.0, 88.0, 99.0),
(7, 'f', 'Helen', 'Davis', 79.0, 83.0, 91.0),
(8, 'm', 'Andrew', 'Johnson', 81.0, 86.0, 88.0);

查询

1、查询所有字段

SELECT * FROM grade;

2、查询grade表中的id,firstname,lastname字段

SELECT id, firstname, lastname FROM grade;

3、查询grade表中id大于4的学生姓名

SELECT firstname, lastname FROM grade WHERE id > 4;

4、查询grade表中女生的记录

SELECT * FROM grade WHERE sex = 'f';

5、查询grade表中id值为2,4,6的学生记录

SELECT * FROM grade WHERE id IN (2, 4, 6);

6、查询grade表中math成绩在85到94之间的记录

SELECT * FROM grade WHERE math BETWEEN 85 AND 94;

7、查询grade表中firstname以A开头的记录

SELECT * FROM grade WHERE firstname LIKE 'A%';

8、查询grade表中firstname以A开头以e结尾的记录

SELECT * FROM grade WHERE firstname LIKE 'A%e';

9、查询grade表中firstname包含l的记录

SELECT * FROM grade WHERE firstname LIKE '%l%';

10、查询grade表中firstname以A开头后面有4个字符的记录

SELECT * FROM grade WHERE firstname LIKE 'A____';

11、查询grade表中english在80到90之间的记录

SELECT * FROM grade WHERE english BETWEEN 80 AND 90;

12、查询grade表中math大于90 或者 chinese大于90的记录

SELECT * FROM grade WHERE math > 90 OR chinese > 90;

13、查询grade表中id不是1、3、5、7的记录

SELECT * FROM grade WHERE id NOT IN (1, 3, 5, 7);

14、查询grade表中的性别有哪些

SELECT DISTINCT sex FROM grade;

15、查询grade表中的lastname有哪几种

SELECT DISTINCT lastname FROM grade;

16、求出表中所有记录的条数

SELECT COUNT(*) FROM grade;

17、求出表中英语成绩的80的记录的条数

SELECT COUNT(*) FROM grade WHERE english = 80;

18、计算所有学生的数学成绩的和

SELECT SUM(math) FROM grade;

19、计算女生的数学成绩的和

SELECT SUM(math) FROM grade WHERE sex = 'f';

20、计算英语成绩平均分

SELECT AVG(english) FROM grade;

21、计算男生的英语成绩平均分

SELECT AVG(english) FROM grade WHERE sex = 'm';

22、求出数学成绩的最高分

SELECT MAX(math) FROM grade;

23、求出男生中的数学最高分

SELECT MAX(math) FROM grade WHERE sex = 'm';

24、按照math成绩的升序进行排列

SELECT * FROM grade ORDER BY math ASC;

25、按照sex字段的升序和chinese字段的降序排列

SELECT * FROM grade ORDER BY sex ASC, chinese DESC;

26、查询数据表grade中的记录，按照sex字段进行分组

SELECT sex, COUNT(*) FROM grade GROUP BY sex;

27、将grade表按照lastname字段值分组，并计算每个分组中的学生数

SELECT lastname, COUNT(*) FROM grade GROUP BY lastname;

28、对grade表按照lastname字段分组，查出math字段和小于100的组

SELECT lastname, SUM(math) AS total_math FROM grade GROUP BY lastname HAVING total_math < 100;

29、查询grade表中的第3到第6条记录

SELECT * FROM grade LIMIT 2, 4;

30、查询grade表中男生平均成绩(三科)大于85的记录

SELECT *, (english + math + chinese) / 3 AS avg_grade FROM grade 
WHERE sex = 'm' HAVING avg_grade > 85;