经典mysql语句实战47练（学生-教师-课程-成绩）

已于 2023-02-09 15:08:10 修改
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经典mysql语句实战47练（学生-教师-课程-成绩）

创建四张表（student、teacher、course、score）

-- 创建student表，插入数据


SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `学号` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `姓名` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `出生日期` timestamp(0) NOT NULL,
  `性别` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '学生表' ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('0001', '猴子', '1989-01-01 00:00:00', '男');
INSERT INTO `student` VALUES ('0002', '猴子', '1990-12-21 00:00:00', '女');
INSERT INTO `student` VALUES ('0003', '马云', '1991-12-21 00:00:00', '男');
INSERT INTO `student` VALUES ('0004', '王思聪', '1990-05-20 00:00:00', '男');

SET FOREIGN_KEY_CHECKS = 1;

-- 创建teacher表，插入数据



SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for teacher
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher`  (
  `教师号` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `教师姓名` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '教师表' ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES ('0001', '孟扎扎');
INSERT INTO `teacher` VALUES ('0002', '马化腾');
INSERT INTO `teacher` VALUES ('0003', NULL);
INSERT INTO `teacher` VALUES ('0004', '');

SET FOREIGN_KEY_CHECKS = 1;

-- 创建course表，插入数据



SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`  (
  `课程号` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `课程名称` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `教师号` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '课程表' ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES ('0001', '语文', '0002');
INSERT INTO `course` VALUES ('0002', '数学', '0001');
INSERT INTO `course` VALUES ('0003', '英语', '0003');

SET FOREIGN_KEY_CHECKS = 1;

-- 创建score表，插入数据



SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for score
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score`  (
  `学号` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `课程号` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,
  `成绩` float NOT NULL
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '成绩表' ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES ('0001', '0001', 80);
INSERT INTO `score` VALUES ('0001', '0002', 90);
INSERT INTO `score` VALUES ('0001', '0003', 99);
INSERT INTO `score` VALUES ('0002', '0002', 60);
INSERT INTO `score` VALUES ('0002', '0003', 80);
INSERT INTO `score` VALUES ('0003', '0001', 80);
INSERT INTO `score` VALUES ('0003', '0002', 80);
INSERT INTO `score` VALUES ('0003', '0003', 80);

SET FOREIGN_KEY_CHECKS = 1;

编写sql语句

-- 1.查询姓“孟”老师的个数
SELECT
	count(教师姓名) 
FROM
	teacher 
WHERE
	教师姓名 LIKE '孟%';

-- 2.查询课程编号为“0002”的总成绩
SELECT
	sum(成绩) 
FROM
	score 
WHERE
	课程号 = '0002';

-- 3.查询选了课程的学生人数
SELECT
	count( DISTINCT 学号 ) AS 学生人数 
FROM
	score;

-- 4.查询各科成绩最高和最低的分， 以如下的形式显示：课程号，最高分，最低分
SELECT
	课程号,
	max(成绩) AS 最高分,
	min(成绩) AS 最低分 
FROM
	score 
GROUP BY
	课程号;

-- 5.查询每门课程被选修的学生数
SELECT
	课程号,
	count(学号) 
FROM
	score 
GROUP BY
	课程号;

-- 6.查询男生、女生人数
SELECT
	性别,
	count(*) 
FROM
	student 
GROUP BY
	性别;

-- 7.查询平均成绩大于60分学生的学号和平均成绩
SELECT
	学号,
	avg(成绩) 
FROM
	score 
GROUP BY
	学号 
HAVING
	avg(成绩)> 60;

-- 8.查询至少选修两门课程的学生学号
SELECT
	学号,
	count(课程号) AS 选修课程数目 
FROM
	score 
GROUP BY
	学号 
HAVING
	count(课程号)>= 2;

-- 9.查询同名同姓学生名单并统计同名人数
SELECT
	姓名,
	count(*) AS 人数 
FROM
	student 
GROUP BY
	姓名 
HAVING
	count(*)>= 2;

-- 10.查询不及格的课程并按课程号从大到小排列
SELECT
	课程号 
FROM
	score 
WHERE
	成绩 < 60 
ORDER BY
	课程号 DESC;

-- 11.查询每门课程的平均成绩，结果按平均成绩升序排序，平均成绩相同时，按课程号降序排列
SELECT
	课程号,
	avg(成绩) AS 平均成绩 
FROM
	score 
GROUP BY
	课程号 
ORDER BY
	平均成绩 ASC,课程号 DESC;

-- 12.检索课程编号为“0004”且分数小于60的学生学号，结果按按分数降序排列
SELECT
	学号 
FROM
	score 
WHERE
	课程号 = '04' 
	AND 成绩 < 60 
ORDER BY
	成绩 DESC;

-- 13.统计每门课程的学生选修人数(超过2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序，若人数相同，按课程号升序排序
SELECT
	课程号,
	count(学号) AS '选修人数' 
FROM
	score 
GROUP BY
	课程号 
HAVING
	count(学号)> 2 
ORDER BY
	count(学号) DESC,课程号 ASC;

-- 14.查询两门以上不及格课程的同学的学号及其平均成绩
SELECT
	学号,
	avg(成绩) AS 平均成绩 
FROM
	score 
WHERE
	成绩 < 60 
GROUP BY
	学号 
HAVING
	count(课程号)> 2;

-- 15.查询学生的总成绩并进行排名
SELECT
	学号,
	sum(成绩) 
FROM
	score 
GROUP BY
	学号 
ORDER BY
	sum(成绩);

-- 16.查询平均成绩大于60分的学生的学号和平均成绩
SELECT 学号, avg(成绩) FROM score GROUP BY 学号 HAVING avg(成绩 ) > 60;

-- 17.查询所有课程成绩小于60分学生的学号、姓名
SELECT
	学号,姓名 
FROM
	student 
WHERE
	学号 IN ( SELECT 学号 FROM score WHERE 成绩 < 60 );

-- 18.查询没有学全所有课的学生的学号、姓名
SELECT
	学号,姓名 
FROM
	student 
WHERE
	学号 IN ( SELECT 学号 FROM score GROUP BY 学号 HAVING count(课程号) < ( SELECT count(课程号) FROM course ) );

-- 19.查询出只选修了两门课程的全部学生的学号和姓名
SELECT
	学号,姓名 
FROM
	student 
WHERE
	学号 IN ( SELECT 学号 FROM score GROUP BY 学号 HAVING count(课程号)= 2 );

-- 20.1990年出生的学生名单
SELECT
	学号,姓名 
FROM
	student 
WHERE
	YEAR (出生日期)= 1990;

-- 21.查询各学生的年龄（精确到月份）
SELECT
	学号,
	timestampdiff(
		MONTH,出生日期,
	now()) 
FROM
	student;

-- 22.查询本月过生日的学生
SELECT
	* 
FROM
	student 
WHERE
	MONTH (出生日期)= MONTH ( CURRENT_DATE );

-- 23.查询所有学生的学号、姓名、选课数、总成绩
SELECT
	a.学号,
	a.姓名,
	count( b.课程号 ) AS 选课数,
	sum( b.成绩 ) AS 总成绩 
FROM
	student AS a
	LEFT JOIN score AS b ON a.学号 = b.学号 
GROUP BY
	a.学号,
	a.姓名;

-- 24.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
	a.学号,
	a.姓名,
	avg( b.成绩 ) AS 平均成绩 
FROM
	student AS a
	LEFT JOIN score AS b ON a.学号 = b.学号 
GROUP BY
	a.学号,
	a.姓名 
HAVING
	avg( b.成绩 )> 85;

-- 25.查询学生的选课情况：学号，姓名，课程号，课程名称
SELECT
	a.学号,
	a.姓名,
	c.课程号,
	c.课程名称 
FROM
	student a
	INNER JOIN score b ON a.学号 = b.学号
	INNER JOIN course c ON b.课程号 = c.课程号;

-- 26.查询出每门课程的及格人数和不及格人数
SELECT 课程号, sum( CASE WHEN 成绩 >= 60 THEN
		1 ELSE 0 
		END 
			) AS 及格人数,
		sum( CASE WHEN 成绩 < 60 THEN 1 ELSE 0 END ) AS 不及格人数 
	FROM
		score 
	GROUP BY
	课程号;

-- 27.使用分段[100-85],[85-70],[70-60],[<60]来统计各科成绩，分别统计：各分数段人数，课程号和课程名称
SELECT
	a.课程号,
	b.课程名称,
	sum( CASE WHEN 成绩 BETWEEN 85 AND 100 THEN 1 ELSE 0 END ) AS '[100-85]',
	sum( CASE WHEN 成绩 >= 70 AND 成绩 < 85 THEN 1 ELSE 0 END ) AS '[85-70]',
	sum( CASE WHEN 成绩 >= 60 AND 成绩 < 70 THEN 1 ELSE 0 END ) AS '[70-60]',
	sum( CASE WHEN 成绩 < 60 THEN 1 ELSE 0 END ) AS '[<60]' 
FROM
	score AS a
	RIGHT JOIN course AS b ON a.课程号 = b.课程号 
GROUP BY
	a.课程号,
	b.课程名称;

-- 28.查询课程编号为0003且课程成绩在80分以上的学生的学号和姓名
SELECT
	a.学号,
	a.姓名 
FROM
	student AS a
	INNER JOIN score AS b ON a.学号 = b.学号 
WHERE
	b.课程号 = '0003' 
	AND b.成绩 > 80;

-- 29.检索"0001"课程分数小于60，按分数降序排列的学生信息
SELECT
	a.*,
	b.成绩 
FROM
	student AS a
	INNER JOIN score AS b ON a.学号 = b.学号 
WHERE
	b.成绩 < 60 
	AND b.课程号 = 01 
ORDER BY
	b.成绩 DESC;

-- 30.查询不同老师所教不同课程平均分从高到低显示
SELECT
	a.教师号,
	a.教师姓名,
	avg( c.成绩 ) 
FROM
	teacher AS a
	INNER JOIN course AS b ON a.教师号 = b.教师号
	INNER JOIN score AS c ON b.课程号 = c.课程号 
GROUP BY
	a.教师号,
	a.教师姓名 
ORDER BY
	avg( c.成绩 ) DESC;

-- 31.查询课程名称为"数学"，且分数低于60的学生姓名和分数
SELECT
	a.姓名,
	b.成绩 
FROM
	student AS a
	INNER JOIN score AS b ON a.学号 = b.学号
	INNER JOIN course c ON b.课程号 = c.课程号 
WHERE
	b.成绩 < 60 
	AND c.课程名称 = '数学';

-- 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（与上题类似）
SELECT
	a.姓名,
	c.课程名称,
	b.成绩 
FROM
	student AS a
	INNER JOIN score AS b ON a.学号 = b.学号
	INNER JOIN course c ON b.课程号 = c.课程号 
WHERE
	b.成绩 > 70;

-- 33.查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩
SELECT
	b.姓名,
	avg( a.成绩 ),
	a.学号 
FROM
	score AS a
	INNER JOIN student AS b ON a.学号 = b.学号 
WHERE
	a.成绩 < 60 GROUP BY b.姓名, a.学号 HAVING count( a.学号 ) >= 2

-- 34.查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩
SELECT DISTINCT
	a.学号,
	a.成绩,
	a.课程号 
FROM
	score AS a
	INNER JOIN score AS b ON a.学号 = b.学号 
WHERE
	a.成绩 = b.成绩 
	AND a.课程号 != b.课程号;

-- 35.查询课程编号为“0001”的课程比“0002”的课程成绩高的所有学生的学号
SELECT
	a.学号 ​ 
FROM
	( SELECT 学号,成绩 FROM score WHERE 课程号 = '0001' ) AS a
	INNER JOIN ( SELECT 学号,成绩 FROM score WHERE 课程号 = '0002' ) AS b ON a.学号 = b.学号
	INNER JOIN student c ON c.学号 = a.学号 
WHERE
	a.成绩 > b.成绩;

-- 36.查询学过编号为“0001”的课程并且也学过编号为“0002”的课程的学生的学号、姓名
SELECT
	c.学号,
	c.姓名 
FROM
	( SELECT 学号, 成绩 FROM score WHERE 课程号 = '0001' ) AS a
	INNER JOIN ( SELECT 学号 FROM score WHERE 课程号 = '0002' ) AS b ON a.学号 = b.学号
	INNER JOIN student AS c ON a.学号 = c.学号;

-- 37.查询学过“孟扎扎”老师所教的所有课的同学的学号、姓名
SELECT
	s.学号,
	s.姓名,
	a.学号,
	b.课程号,
	c.教师号,
	c.教师姓名 
FROM
	student AS s
	INNER JOIN score AS a ON s.学号 = a.学号
	INNER JOIN course b ON a.课程号 = b.课程号
	INNER JOIN teacher c ON b.教师号 = c.教师号 
WHERE
	c.教师姓名 = '孟扎扎';

-- 38.查询没学过"孟扎扎"老师讲授的任一门课程的学生姓名（与上题类似，"没学过"用not in来实现)
SELECT
	姓名,学号 
FROM
	student 
WHERE
	学号 NOT IN (
	SELECT
		a.学号 
	FROM
		student AS a
		INNER JOIN score AS b ON a.学号 = b.学号
		INNER JOIN course AS c ON b.课程号 = c.课程号
		INNER JOIN teacher AS d ON c.教师号 = d.教师号 
	WHERE
		d.教师姓名 = '孟扎扎' 
	);

-- 39.查询没学过“孟扎扎”老师课的学生的学号、姓名（与上题类似）
SELECT
	学号,
	姓名 
FROM
	student 
WHERE
	学号 NOT IN ( SELECT 学号 FROM score WHERE 课程号 = ( SELECT 课程号 FROM course WHERE 教师号 = ( SELECT 教师号 FROM teacher WHERE 教师姓名 = '孟扎扎' ) ) );

-- 40.查询选修“孟扎扎”老师所授课程的学生中成绩最高的学生姓名及其成绩（与上题类似,用成绩排名，用 limit 1得出最高一个）
SELECT
	a.姓名,
	b.成绩 
FROM
	student AS a
	INNER JOIN score AS b ON a.学号 = b.学号
	INNER JOIN course AS c ON b.课程号 = c.课程号
	INNER JOIN teacher AS d ON c.教师号 = d.教师号 
WHERE
	d.教师姓名 = '孟扎扎' 
ORDER BY
	b.成绩 DESC 
	LIMIT 1;

-- 41.查询至少有一门课与学号为“0001”的学生所学课程相同的学生的学号和姓名
SELECT
	学号,姓名 
FROM
	student ​​ 
WHERE
	学号 IN (
	SELECT DISTINCT
		(学号) 
	FROM
		score 
	WHERE
	课程号 IN ( SELECT 课程号 FROM score WHERE 学号 = '0001' )) 
	AND 学号 != '0001';

-- 42.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩
SELECT
	a.学号,
	avg( a.成绩 ),
	max( CASE WHEN b.课程名称 = '数学' THEN a.成绩 ELSE NULL END ) AS '数学',
	max( CASE WHEN b.课程名称 = '语文' THEN a.成绩 ELSE NULL END ) AS '语文',
	max( CASE WHEN b.课程名称 = '英语' THEN a.成绩 ELSE NULL END ) AS '英语' 
FROM
	score AS a
	INNER JOIN course AS b ON a.课程号 = b.课程号 
GROUP BY
	a.学号;

-- 43.查询学生平均成绩及其名次
SELECT
	学号,
	avg(成绩),
	row_number () over ( ORDER BY avg(成绩) DESC ) 
FROM
	score 
GROUP BY
	学号  ;

-- 44.按各科成绩进行排序，并显示排名
SELECT
	课程号,
	row_number () over ( PARTITION BY 课程号 ORDER BY 成绩 ) 
FROM
	score;

-- 45.查询每门功成绩最好的前两名学生姓名
SELECT
	a.课程号,
	b.姓名,
	a.成绩,
	a.ranking​ 
FROM
	( SELECT 课程号,学号,成绩, row_number () over ( PARTITION BY 课程号 ORDER BY 成绩 DESC ) AS ranking​ FROM score ) AS a
	INNER JOIN student b ON a.学号 = b.学号 
WHERE
	a.ranking​ < 3;

-- 46.查询所有课程的成绩第2名到第3名的学生信息及该课程成绩（与上一题相似）
SELECT
	b.姓名,
	a.课程号,
	a.成绩 ​​ 
FROM
	( SELECT 课程号,学号,成绩, row_number () over ( PARTITION BY 课程号 ORDER BY 成绩 DESC ) AS ranking FROM score ) AS a
	INNER JOIN student AS b ON a.学号 = b.学号 
WHERE
	a.ranking IN ( 2, 3 );

-- 47.查询各科成绩前三名的记录（不考虑成绩并列情况）（与上一题相似）
SELECT
	b.姓名,
	a.课程号,
	a.成绩 
FROM
	( SELECT 课程号,学号,成绩, row_number () over ( PARTITION BY 课程号 ORDER BY 成绩 DESC ) AS 'ranking' FROM score ) AS a
	INNER JOIN student AS b ON a.学号 = b.学号 
WHERE
	a.ranking < 4;
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