20200325 数据库连接查询面试题作业

本节课作业：

#6 查询出语文最高分

#8 查询语数外三门成绩的平均分

#9 查询报名孤独求败老师课程的学生信息

表结构：

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`  (
  `Cno` int(11) NOT NULL COMMENT '课程编号',
  `Cname` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '课程名称',
  `Tno` int(11) NULL DEFAULT NULL COMMENT '老师编号',
  PRIMARY KEY (`Cno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES (1, '数学', 1);
INSERT INTO `course` VALUES (2, '语文', 2);
INSERT INTO `course` VALUES (3, '英文', 1);

-- ----------------------------
-- Table structure for sc
-- ----------------------------
DROP TABLE IF EXISTS `sc`;
CREATE TABLE `sc`  (
  `Sno` int(11) NOT NULL COMMENT '学号',
  `Cno` int(11) NOT NULL COMMENT '课程编号',
  `score` int(255) NULL DEFAULT NULL COMMENT '分数',
  PRIMARY KEY (`Sno`, `Cno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

-- ----------------------------
-- Records of sc
-- ----------------------------
INSERT INTO `sc` VALUES (1, 1, 99);
INSERT INTO `sc` VALUES (1, 2, 80);
INSERT INTO `sc` VALUES (1, 3, 50);
INSERT INTO `sc` VALUES (2, 1, 70);
INSERT INTO `sc` VALUES (2, 2, 90);
INSERT INTO `sc` VALUES (3, 1, 90);
INSERT INTO `sc` VALUES (4, 1, 60);
INSERT INTO `sc` VALUES (4, 2, 50);
INSERT INTO `sc` VALUES (4, 3, 40);

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `Sno` int(255) NOT NULL COMMENT '学号',
  `Sname` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '姓名',
  `Sage` int(255) NULL DEFAULT NULL COMMENT '年龄',
  `Ssex` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '性别',
  PRIMARY KEY (`Sno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '张三丰', 108, '男');
INSERT INTO `student` VALUES (2, '李小龙', 20, '男');
INSERT INTO `student` VALUES (3, '小龙女', 17, '女');
INSERT INTO `student` VALUES (4, '白发魔女', 18, '女');
INSERT INTO `student` VALUES (5, '韦小宝', 19, '男');

-- ----------------------------
-- Table structure for teacher
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher`  (
  `Tno` int(11) NOT NULL COMMENT '老师编号',
  `Tname` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '老师名称',
  PRIMARY KEY (`Tno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES (1, '无崖子');
INSERT INTO `teacher` VALUES (2, '孤独求败');
INSERT INTO `teacher` VALUES (3, '洪七公');

SET FOREIGN_KEY_CHECKS = 1;

实战sql：

# 15 - 20 
#1 查询年龄小于18岁的学员信息 (5)
select * from student a where a.Sage < 18;
#2 查询无崖子授课信息
select * from teacher d 
INNER JOIN course c on d.Tno = c.Tno
where d.TName = '无崖子';
#3 查询没有参与任意课程的学生信息
select * from student a LEFT JOIN sc b on a.Sno = b.Sno 
where b.Sno is null;
#4 查询无崖子每个授课课程的学员人数 统计 + 分组 
select c.Cno,c.Cname,count(*) from teacher d 
INNER JOIN course c on d.Tno = c.Tno 
INNER JOIN sc b on b.Cno = c.Cno 
where d.TName = '无崖子'
GROUP BY c.Cno,c.Cname;
#5 查询张三丰数学成绩
select * from student a INNER JOIN sc b on a.Sno = b.Sno
INNER JOIN course c on c.Cno = b.Cno
where a.Sname = '张三丰' and c.Cname = '数学';

#6 查询出语文最高分

#7 查询没有参与语文考试的学生信息
# 先查询出参加了语文课程学生
select * from course c 
INNER JOIN sc b on c.Cno = b.Cno and c.Cname = '语文'
RIGHT JOIN Student a on a.Sno = b.Sno 
where b.Sno is null;
# 和学生做外连接
#8 查询语数外三门成绩的平均分 

#9 查询报名孤独求败老师课程的学生信息

#10 没有报名孤独求败老师课程的学生信息
select * from teacher d 
INNER JOIN course c on d.Tno = c.Tno and d.Tname = '孤独求败'
INNER JOIN sc b on c.Cno = b.Cno
RIGHT JOIN Student a on a.Sno = b.Sno 
where b.Sno is null;

59 回帖

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luojie • 4 年前作者

满分~~~~！
其他回帖
sunicequeen • 4 年前

本节课作业：
#6 查询出语文最高分
select Max(score) from SC b
inner join Course c on b.Cno=c.Cno
where c.Cname="语文";
#8 查询语数外三门成绩的平均分
select avg(score) from sc b
inner join course c on b.Cno=c.Cno
group by c.Cno
#9 查询报名孤独求败老师课程的学生信息
select * from teacher d
inner join course c on d.Tno=c.Tno
and d.Tname="孤独求败"
inner joinsc b on c.Cno=b.Cno
right join Student a on a.Sno=b.Sno;
youmaobing233 • 4 年前

1：
select MAX(score) from sc s inner join course c on s.Cno = c.Cno and c.Cname = '语文'

2：
select AVG(s.score),c.Cname from sc s inner join course c on s.Cno = c.Cno
GROUP BY c.Cname;

3：
SELECT * from student s inner join sc c on s.Sno = c.Sno
inner join course r on r.Cno = c.Cno
inner join teacher t on t.Tno = r.Tno where t.Tname = '孤独求败'
zoe • 4 年前

#6 查询出语文最高分
SELECT MAX(sc.score),course.Cname from lemon_sc as sc INNER JOIN lemon_course as course on course.Cno=sc.Cno and course.Cname like '%语文'

#8 查询语数外三门成绩的平均分
SELECT AVG(sc.score),course.Cname from lemon_sc as sc INNER JOIN lemon_course as course on course.Cno=sc.Cno GROUP BY course.Cno

#9 查询报名孤独求败老师课程的学生信息
SELECT stu.* from lemon_student as stu INNER JOIN lemon_sc as sc on stu.Sno=sc.Sno INNER JOIN lemon_course as cou on sc.Cno=cou.Cno INNER JOIN lemon_teacher as tea on tea.Tno=cou.Tno where tea.Tname ='孤独求败'
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