Mysql 测试题
一. 表结构和数据
/*
Navicat Premium Data Transfer Source Server : localhost
Source Server Type : MySQL
Source Server Version : 50624
Source Host : localhost
Source Database : sqlexam Target Server Type : MySQL
Target Server Version : 50624
File Encoding : utf-8 Date: 10/21/2016 06:46:46 AM
*/ SET NAMES utf8;
SET FOREIGN_KEY_CHECKS = 0; -- ----------------------------
-- Table structure for `class`
-- ----------------------------
DROP TABLE IF EXISTS `class`;
CREATE TABLE `class` (
`cid` int(11) NOT NULL AUTO_INCREMENT,
`caption` varchar(32) NOT NULL,
PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ----------------------------
-- Records of `class`
-- ----------------------------
BEGIN;
INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班');
COMMIT; -- ----------------------------
-- Table structure for `course`
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
`cid` int(11) NOT NULL AUTO_INCREMENT,
`cname` varchar(32) NOT NULL,
`teacher_id` int(11) NOT NULL,
PRIMARY KEY (`cid`),
KEY `fk_course_teacher` (`teacher_id`),
CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ----------------------------
-- Records of `course`
-- ----------------------------
BEGIN;
INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2');
COMMIT; -- ----------------------------
-- Table structure for `score`
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
`sid` int(11) NOT NULL AUTO_INCREMENT,
`student_id` int(11) NOT NULL,
`course_id` int(11) NOT NULL,
`num` int(11) NOT NULL,
PRIMARY KEY (`sid`),
KEY `fk_score_student` (`student_id`),
KEY `fk_score_course` (`course_id`),
CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`),
CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8; -- ----------------------------
-- Records of `score`
-- ----------------------------
BEGIN;
INSERT INTO `score` VALUES ('1', '1', '1', '10'), ('2', '1', '2', '9'), ('5', '1', '4', '66'), ('6', '2', '1', '8'), ('8', '2', '3', '68'), ('9', '2', '4', '99'), ('10', '3', '1', '77'), ('11', '3', '2', '66'), ('12', '3', '3', '87'), ('13', '3', '4', '99'), ('14', '4', '1', '79'), ('15', '4', '2', '11'), ('16', '4', '3', '67'), ('17', '4', '4', '100'), ('18', '5', '1', '79'), ('19', '5', '2', '11'), ('20', '5', '3', '67'), ('21', '5', '4', '100'), ('22', '6', '1', '9'), ('23', '6', '2', '100'), ('24', '6', '3', '67'), ('25', '6', '4', '100'), ('26', '7', '1', '9'), ('27', '7', '2', '100'), ('28', '7', '3', '67'), ('29', '7', '4', '88'), ('30', '8', '1', '9'), ('31', '8', '2', '100'), ('32', '8', '3', '67'), ('33', '8', '4', '88'), ('34', '9', '1', '91'), ('35', '9', '2', '88'), ('36', '9', '3', '67'), ('37', '9', '4', '22'), ('38', '10', '1', '90'), ('39', '10', '2', '77'), ('40', '10', '3', '43'), ('41', '10', '4', '87'), ('42', '11', '1', '90'), ('43', '11', '2', '77'), ('44', '11', '3', '43'), ('45', '11', '4', '87'), ('46', '12', '1', '90'), ('47', '12', '2', '77'), ('48', '12', '3', '43'), ('49', '12', '4', '87'), ('52', '13', '3', '87');
COMMIT; -- ----------------------------
-- Table structure for `student`
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`sid` int(11) NOT NULL AUTO_INCREMENT,
`gender` char(1) NOT NULL,
`class_id` int(11) NOT NULL,
`sname` varchar(32) NOT NULL,
PRIMARY KEY (`sid`),
KEY `fk_class` (`class_id`),
CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8; -- ----------------------------
-- Records of `student`
-- ----------------------------
BEGIN;
INSERT INTO `student` VALUES ('1', '男', '1', '理解'), ('2', '女', '1', '钢蛋'), ('3', '男', '1', '张三'), ('4', '男', '1', '张一'), ('5', '女', '1', '张二'), ('6', '男', '1', '张四'), ('7', '女', '2', '铁锤'), ('8', '男', '2', '李三'), ('9', '男', '2', '李一'), ('10', '女', '2', '李二'), ('11', '男', '2', '李四'), ('12', '女', '3', '如花'), ('13', '男', '3', '刘三'), ('14', '男', '3', '刘一'), ('15', '女', '3', '刘二'), ('16', '男', '3', '刘四');
COMMIT; -- ----------------------------
-- Table structure for `teacher`
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
`tid` int(11) NOT NULL AUTO_INCREMENT,
`tname` varchar(32) NOT NULL,
PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; -- ----------------------------
-- Records of `teacher`
-- ----------------------------
BEGIN;
INSERT INTO `teacher` VALUES ('1', '张磊老师'), ('2', '李平老师'), ('3', '刘海燕老师'), ('4', '朱云海老师'), ('5', '李杰老师');
COMMIT; SET FOREIGN_KEY_CHECKS = 1; 表结构和数据
SQL 表结构和数据
create database homework default character set utf8 collate utf8_general_ci; MariaDB [homework]> show tables;
+--------------------+
| Tables_in_homework |
+--------------------+
| class |
| course |
| score |
| student |
| teacher |
+--------------------+
rows in set (0.00 sec) MariaDB [homework]> select * from class;
+-----+--------------+
| cid | caption |
+-----+--------------+
| | 三年二班 |
| | 三年三班 |
| | 一年二班 |
| | 二年九班 |
+-----+--------------+
rows in set (0.00 sec) MariaDB [homework]> select * from student;
+-----+--------+----------+--------+
| sid | gender | class_id | sname |
+-----+--------+----------+--------+
| | 男 | | 理解 |
| | 女 | | 钢蛋 |
| | 男 | | 张三 |
| | 男 | | 张一 |
| | 女 | | 张二 |
| | 男 | | 张四 |
| | 女 | | 铁锤 |
| | 男 | | 李三 |
| | 男 | | 李一 |
| | 女 | | 李二 |
| | 男 | | 李四 |
| | 女 | | 如花 |
| | 男 | | 刘三 |
| | 男 | | 刘一 |
| | 女 | | 刘二 |
| | 男 | | 刘四 |
+-----+--------+----------+--------+
rows in set (0.01 sec) MariaDB [homework]> select * from teacher;
+-----+-----------------+
| tid | tname |
+-----+-----------------+
| | 张磊老师 |
| | 李平老师 |
| | 刘海燕老师 |
| | 朱云海老师 |
| | 李杰老师 |
+-----+-----------------+
rows in set (0.00 sec) MariaDB [homework]> select * from course;
+-----+--------+------------+
| cid | cname | teacher_id |
+-----+--------+------------+
| | 生物 | |
| | 物理 | |
| | 体育 | |
| | 美术 | |
+-----+--------+------------+
rows in set (0.00 sec) MariaDB [homework]> select * from score;
+-----+------------+-----------+-----+
| sid | student_id | course_id | num |
+-----+------------+-----------+-----+
| | | | |
| | | | |
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+-----+------------+-----------+-----+
rows in set (0.00 sec)
表内容
二、操作表
1、自行创建测试数据
2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
#先查出生物和物理
select score.sid,score.student_id,course.cname,score.num from score left join course on score.course_id = course.cid where course.cname="生物";
select score.sid,score.student_id,course.cname,score.num from score left join course on score.course_id = course.cid where course.cname="物理"; select A.student_id from (select score.sid,score.student_id,course.cname,score.num from score left join course on score.course_id = course.cid where course.cname="生物") as A inner join (select score.sid,score.student_id,course.cname,score.num from score left join course on score.course_id = course.cid where course.cname=" 物理") as B on B.student_id= A.student_id where A.num > B.num;
+------------+
| student_id |
+------------+
| 1 |
| 3 |
| 4 |
| 5 |
| 9 |
| 10 |
| 11 |
| 12 |
+------------+
8 rows in set (0.00 sec)
3、查询平均成绩大于60分的同学的学号和平均成绩；
select A.student_id,student.sname,Average from (select student_id,avg(num) as Average from score group by student_id having avg(num) >60) as A LEFT JOIN student ON A.student_id = student.sid;
+------------+--------+---------+
| student_id | sname | Average |
+------------+--------+---------+
| 3 | 张三 | 82.2500 |
| 4 | 张一 | 64.2500 |
| 5 | 张二 | 64.2500 |
| 6 | 张四 | 69.0000 |
| 7 | 铁锤 | 66.0000 |
| 8 | 李三 | 66.0000 |
| 9 | 李一 | 67.0000 |
| 10 | 李二 | 74.2500 |
| 11 | 李四 | 74.2500 |
| 12 | 如花 | 74.2500 |
| 13 | 刘三 | 87.0000 |
+------------+--------+---------+
11 rows in set (0.00 sec)
4、查询所有同学的学号、姓名、选课数、总成绩；
MariaDB [homework]> select score.student_id,student.sname,count(student_id),sum(num) from score LEFT JOIN student on score.student_id=student.sid GROUP BY score.student_id;
+------------+--------+-------------------+----------+
| student_id | sname | count(student_id) | sum(num) |
+------------+--------+-------------------+----------+
| 1 | 理解 | 3 | 85 |
| 2 | 钢蛋 | 3 | 175 |
| 3 | 张三 | 4 | 329 |
| 4 | 张一 | 4 | 257 |
| 5 | 张二 | 4 | 257 |
| 6 | 张四 | 4 | 276 |
| 7 | 铁锤 | 4 | 264 |
| 8 | 李三 | 4 | 264 |
| 9 | 李一 | 4 | 268 |
| 10 | 李二 | 4 | 297 |
| 11 | 李四 | 4 | 297 |
| 12 | 如花 | 4 | 297 |
| 13 | 刘三 | 1 | 87 |
+------------+--------+-------------------+----------+
13 rows in set (0.00 sec)
5、查询姓“李”的老师的个数；
MariaDB [homework]> select count(tid) from teacher where tname like "李%";
+------------+
| count(tid) |
+------------+
| 2 |
+------------+
1 row in set (0.00 sec)
6、查询没学过“叶平”老师课的同学的学号、姓名；
#李平老师选的课程
select cid from course left join teacher on course.teacher_id=teacher.tid where teacher.tname ="李平老师";
#课程里面学过李平老师的学员过滤出来
select score.student_id from score where course_id in (select cid from course left join teacher on course.teacher_id=teacher.tid where teacher.tname ="李平老师") group by score.student_id; SELECT
student.sid,
student.sname
FROM
student
WHERE
sid NOT IN (
SELECT
score.student_id
FROM
score
WHERE
course_id IN (
SELECT
cid
FROM
course
LEFT JOIN teacher ON course.teacher_id = teacher.tid
WHERE
teacher.tname = "李平老师"
)
GROUP BY
score.student_id
);
+-----+--------+
| sid | sname |
+-----+--------+
| 13 | 刘三 |
| 14 | 刘一 |
| 15 | 刘二 |
| 16 | 刘四 |
+-----+--------+
4 rows in set (0.00 sec)
7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
SELECT
A.student_id,
student.sname
FROM
(
SELECT
*
FROM
score
WHERE
course_id IN (1, 2)
) AS A
LEFT JOIN student ON student.sid = A.student_id
GROUP BY
A.student_id
HAVING
count(A.student_id) > 1; +------------+--------+
| student_id | sname |
+------------+--------+
| 1 | 理解 |
| 3 | 张三 |
| 4 | 张一 |
| 5 | 张二 |
| 6 | 张四 |
| 7 | 铁锤 |
| 8 | 李三 |
| 9 | 李一 |
| 10 | 李二 |
| 11 | 李四 |
| 12 | 如花 |
+------------+--------+
11 rows in set (0.00 sec)
8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
SELECT student_id, student.sname FROM score LEFT JOIN student ON student.sid = score.student_id WHERE course_id IN ( SELECT cid FROM course WHERE teacher_id = ( SELECT tid FROM teacher WHERE tname = "李平老师" )) GROUP BY student_id HAVING COUNT(1) = ( SELECT COUNT(cid) FROM course WHERE teacher_id = ( SELECT tid FROM teacher WHERE tname = "李平老师" ));
9、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；
SELECT
student_id,
student.sname
FROM
(
SELECT
A.student_id
FROM
(
SELECT
*
FROM
score
WHERE
course_id = 1
) AS A
INNER JOIN (
SELECT
*
FROM
score
WHERE
course_id = 2
) AS B ON A.student_id = B.student_id
WHERE
A.num > B.num
) AS C
LEFT JOIN student ON C.student_id = student.sid; +------------+--------+
| student_id | sname |
+------------+--------+
| 1 | 理解 |
| 3 | 张三 |
| 4 | 张一 |
| 5 | 张二 |
| 9 | 李一 |
| 10 | 李二 |
| 11 | 李四 |
| 12 | 如花 |
+------------+--------+
8 rows in set (0.00 sec)
10、查询有课程成绩小于60分的同学的学号、姓名；
SELECT
score.student_id,
student.sname
FROM
score
LEFT JOIN student ON student.sid = score.student_id
WHERE
score.num < 60
GROUP BY
score.student_id; +------------+--------+
| student_id | sname |
+------------+--------+
| 1 | 理解 |
| 2 | 钢蛋 |
| 4 | 张一 |
| 5 | 张二 |
| 6 | 张四 |
| 7 | 铁锤 |
| 8 | 李三 |
| 9 | 李一 |
| 10 | 李二 |
| 11 | 李四 |
| 12 | 如花 |
+------------+--------+
11 rows in set (0.00 sec)
11、查询没有学全所有课的同学的学号、姓名；
SELECT
score.student_id,
student.sname
FROM
score
LEFT JOIN student ON student.sid = score.student_id
GROUP BY
score.student_id
HAVING
count(score.student_id) < (SELECT count(*) FROM course); +------------+--------+
| student_id | sname |
+------------+--------+
| 3 | 张三 |
| 4 | 张一 |
| 5 | 张二 |
| 6 | 张四 |
| 7 | 铁锤 |
| 8 | 李三 |
| 9 | 李一 |
| 10 | 李二 |
| 11 | 李四 |
| 12 | 如花 |
+------------+--------+
10 rows in set (0.00 sec)
12、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名；
SELECT
student_id,
student.sname
FROM
score
LEFT JOIN student ON student.sid = score.student_id
WHERE
course_id IN (
SELECT
course_id
FROM
score
WHERE
student_id = "1"
)
AND student_id != 1
GROUP BY
(score.student_id); +------------+--------+
| student_id | sname |
+------------+--------+
| 2 | 钢蛋 |
| 3 | 张三 |
| 4 | 张一 |
| 5 | 张二 |
| 6 | 张四 |
| 7 | 铁锤 |
| 8 | 李三 |
| 9 | 李一 |
| 10 | 李二 |
| 11 | 李四 |
| 12 | 如花 |
+------------+--------+
11 rows in set (0.00 sec)
13、查询至少学过学号为“001”同学所选课程中任意一门课的其他同学学号和姓名；
14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名；
15、删除学习“叶平”老师课的SC表记录；
select * from score where course_id in (select cid from course where teacher_id = (select tid from teacher where tname="李平老师"));
16、向SC表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“002”课程的同学学号；②插入“002”号课程的平均成绩；
MariaDB [homework]> select student_id from score where student_id not in (select student_id from score where course_id =(select cid from course where cid=2)) group by student_id;
+------------+
| student_id |
+------------+
| 2 |
| 13 |
+------------+
2 rows in set (0.00 sec)
没成功
17、按平均成绩从低到高显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
18、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 course_id,max(num),min(num) from score left join course on course.cid = score.course_id group by course_id;
+-----------+----------+----------+
| course_id | max(num) | min(num) |
+-----------+----------+----------+
| 1 | 91 | 8 |
| 2 | 100 | 9 |
| 3 | 87 | 43 |
| 4 | 100 | 22 |
+-----------+----------+----------+
4 rows in set (0.00 sec)
19、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；
20、课程平均分从高到低显示（现实任课老师）；
select course.cname,avg(num) from score left join course on course.cid=score.course_id group by course_id order by (avg(num)) desc;
+--------+----------+
| cname | avg(num) |
+--------+----------+
| 美术 | 85.2500 |
| 物理 | 65.0909 |
| 体育 | 64.4167 |
| 生物 | 53.4167 |
+--------+----------+
4 rows in set (0.00 sec)
21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
22、查询每门课程被选修的学生数；
MariaDB [homework]> select course_id,count(student_id) from score group by course_id;
+-----------+-------------------+
| course_id | count(student_id) |
+-----------+-------------------+
| 1 | 12 |
| 2 | 11 |
| 3 | 12 |
| 4 | 12 |
+-----------+-------------------+
4 rows in set (0.00 sec)
23、查询出只选修了一门课程的全部学生的学号和姓名；
select sid,sname from student where sid = (select student_id from score group by student_id having count(student_id) =1);
+-----+--------+
| sid | sname |
+-----+--------+
| 13 | 刘三 |
+-----+--------+
1 row in set (0.00 sec)
24、查询男生、女生的人数；
select gender,count(gender) from student group by gender;
+--------+---------------+
| gender | count(gender) |
+--------+---------------+
| 女 | 6 |
| 男 | 10 |
+--------+---------------+
2 rows in set (0.00 sec)
25、查询姓“张”的学生名单；
select * from student where sname like "张%";
+-----+--------+----------+--------+
| sid | gender | class_id | sname |
+-----+--------+----------+--------+
| 3 | 男 | 1 | 张三 |
| 4 | 男 | 1 | 张一 |
| 5 | 女 | 1 | 张二 |
| 6 | 男 | 1 | 张四 |
+-----+--------+----------+--------+
4 rows in set (0.00 sec)
26、查询同名同姓学生名单，并统计同名人数；
select sname,count(sname) from student group by sname having count(sname) >1;
+--------+--------------+
| sname | count(sname) |
+--------+--------------+
| 张三 | 2 |
| 张二 | 2 |
+--------+--------------+
2 rows in set (0.00 sec)
27、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 course_id,cname,avg(num) from score left join course on course.cid= score.course_id group by course_id order by avg(num) asc,course_id asc;
+-----------+--------+----------+
| course_id | cname | avg(num) |
+-----------+--------+----------+
| 1 | 生物 | 53.4167 |
| 3 | 体育 | 64.4167 |
| 2 | 物理 | 65.0909 |
| 4 | 美术 | 85.2500 |
+-----------+--------+----------+
4 rows in set (0.00 sec)
28、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 student.sid,student.sname,avg(num) from score left join student on student.sid=score.student_id group by score.student_id having avg(num) > 85;
+------+--------+----------+
| sid | sname | avg(num) |
+------+--------+----------+
| 13 | 刘三 | 87.0000 |
+------+--------+----------+
1 row in set (0.00 sec)
29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
select sname,num from score left join student on student.sid=score.student_id where course_id = (select cid from course where cname = "体育") and num < 60;
+--------+-----+
| sname | num |
+--------+-----+
| 李二 | 43 |
| 李四 | 43 |
| 如花 | 43 |
+--------+-----+
3 rows in set (0.00 sec)
30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
select student_id,student.sname from score left join student on student.sid=score.student_id where course_id = (select cid from course where cid=3) and num > 80;
+------------+--------+
| student_id | sname |
+------------+--------+
| 3 | 张三 |
| 13 | 刘三 |
+------------+--------+
2 rows in set (0.00 sec)
31、求选了课程的学生人数
select count(student_id) from (select student_id from score group by student_id) as A;
+-------------------+
| count(student_id) |
+-------------------+
| 13 |
+-------------------+
1 row in set (0.00 sec)
32、查询选修“杨艳”老师所授课程的学生中，成绩最高的学生姓名及其成绩；
select student.sname,num from score left join student on student.sid=score.student_id where course_id in (select cid from course where teacher_id = (select tid from teacher where tname="李平老师")) group by course_id;
+--------+-----+
| sname | num |
+--------+-----+
| 理解 | 9 |
| 理解 | 66 |
+--------+-----+
2 rows in set (0.00 sec)
33、查询各个课程及相应的选修人数；
select course.cname,count(course_id) from score left join course on course.cid=score.course_id group by course_id;
+--------+------------------+
| cname | count(course_id) |
+--------+------------------+
| 生物 | 12 |
| 物理 | 11 |
| 体育 | 12 |
| 美术 | 12 |
+--------+------------------+
4 rows in set (0.00 sec)
34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；
35、查询每门课程成绩最好的前两名；
select sid,student_id,course_id,max(num) from score group by course_id;
+-----+------------+-----------+----------+
| sid | student_id | course_id | max(num) |
+-----+------------+-----------+----------+
| 1 | 1 | 1 | 91 |
| 2 | 1 | 2 | 100 |
| 8 | 2 | 3 | 87 |
| 5 | 1 | 4 | 100 |
+-----+------------+-----------+----------+
4 rows in set (0.00 sec)
没做完
36、检索至少选修两门课程的学生学号；
37、查询全部学生都选修的课程的课程号和课程名；
38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；
39、查询两门以上不及格课程的同学的学号及其平均成绩；
40、检索“004”课程分数小于60，按分数降序排列的同学学号；
41、删除“002”同学的“001”课程的成绩；
7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
-- select score.student_id,student.sname from score
--
-- left join student on score.student_id=student.sid
--
-- where course_id =1 or course_id =2 GROUP BY student_id HAVING count(course_id) > 1 8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
-- select student_id from score where course_id in (
-- select cid from course left JOIN teacher on course.teacher_id = teacher.tid where teacher.tname = "李平老师"
-- ) GROUP BY student_id having count(course_id) = (select count(cid) from course left JOIN teacher on course.teacher_id = teacher.tid where teacher.tname = "李平老师")
--
--
10、查询有课程成绩小于60分的同学的学号、姓名；
-- select student_id from score where num < 60 GROUP BY student_id
-- select DISTINCT student_id from score where num < 60 -- 查询没有学全所有课的同学的学号、姓名； 11、查询没有学全所有课的同学的学号、姓名；
-- select student_id,count(1) from score GROUP BY student_id HAVING count(1) < (select count(cid) from course);
-- -- 12、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名；
-- select course_id from score where student_id = 1;
-- select student_id from score where student_id != 1 and course_id in (select course_id from score where student_id = 1) GROUP BY student_id -- 13、查询至少学过学号为“001”同学所有课的其他同学学号和姓名；
-- select course_id from score where student_id = 1;
-- select student_id,count(1) from score where student_id != 1 and course_id in (select course_id from score where student_id = 1) GROUP BY student_id HAVING count(1) = (select count(course_id) from score where student_id = 1) -- 14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名； -- 获取和方少伟选课个数相同的通许
-- select count(1) from score where student_id = 1;
-- -- select student_id from score where student_id in (
-- select student_id from score where student_id !=1 GROUP BY student_id HAVING count(1) = (select count(1) from score where student_id = 1)
-- ) and course_id in (select course_id from score where student_id = 1) GROUP BY student_id HAVING count(1) = (select count(1) from score where student_id = 1)
--
--
-- insert into tb(student_id,course_id,num)
--
-- select student_id,2,(SELECT AVG(num) from score where course_id = 2) from score where course_id != 2 -- 17、按平均成绩从低到高 显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
-- 1 90 80 99
-- 2 90 80 99
-- SELECT
-- student_id,
-- (select num from score as s2 where s2.student_id=s1.student_id and course_id = 1) as 语文,
-- (select num from score as s2 where s2.student_id=s1.student_id and course_id = 2) as 数学,
-- (select num from score as s2 where s2.student_id=s1.student_id and course_id = 3) as 英语
-- from score as s1;
--
-- 18、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 course_id,max(num),min(num),min(num)+1,case when min(num) <10 THEN 0 ELSE min(num) END as c from score GROUP BY course_id -- 19、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 course_id,avg(num),sum(case when num <60 THEN 0 ELSE 1 END),sum(1),sum(case when num <60 THEN 0 ELSE 1 END)/sum(1) as jgl from score GROUP BY course_id order by AVG(num) asc,jgl desc;
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