MySQL 常用 SQL 语句_`ithuang`.`#sql-1dcc_52`, constraint `f_coursegrad

数据库：

 
    SET FOREIGN_KEY_CHECKS=0;
    -- ----------------------------
    -- Table structure for course
    -- ----------------------------
    DROP TABLE IF EXISTS `course`;
    CREATE TABLE `course` (
      `Cno` int(11) NOT NULL,
      `Cname` varchar(255) CHARACTER SET utf8 DEFAULT NULL,
      `Cpno` int(11) DEFAULT NULL,
      `Ccredit` int(11) DEFAULT NULL,
      PRIMARY KEY (`Cno`)
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
    -- ----------------------------
    -- Records of course
    -- ----------------------------
    INSERT INTO `course` VALUES ('1', '数据库', '5', '4');
    INSERT INTO `course` VALUES ('2', '数学', null, '2');
    INSERT INTO `course` VALUES ('3', '信息系统', '1', '4');
    INSERT INTO `course` VALUES ('4', '操作系统', '6', '3');
    INSERT INTO `course` VALUES ('5', '数据结构', '7', '4');
    INSERT INTO `course` VALUES ('6', '数据处理', null, '2');
    INSERT INTO `course` VALUES ('7', 'PASCAL语言', '6', '4');
    -- ----------------------------
    -- Table structure for sc
    -- ----------------------------
    DROP TABLE IF EXISTS `sc`;
    CREATE TABLE `sc` (
      `Sno` int(11) NOT NULL,
      `Cno` int(11) NOT NULL,
      `Grade` int(11) DEFAULT NULL,
      KEY `FK_cno` (`Cno`),
      KEY `FK_sno` (`Sno`),
      CONSTRAINT `FK_cno` FOREIGN KEY (`Cno`) REFERENCES `course` (`Cno`) ON DELETE CASCADE ON UPDATE CASCADE,
      CONSTRAINT `FK_sno` FOREIGN KEY (`Sno`) REFERENCES `student` (`Sno`) ON DELETE CASCADE ON UPDATE CASCADE
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
    -- ----------------------------
    -- Records of sc
    -- ----------------------------
    INSERT INTO `sc` VALUES ('201215121', '1', '97');
    INSERT INTO `sc` VALUES ('201215121', '2', '90');
    INSERT INTO `sc` VALUES ('201215121', '3', '93');
    INSERT INTO `sc` VALUES ('201215122', '2', '95');
    INSERT INTO `sc` VALUES ('201215122', '3', '85');
    -- ----------------------------
    -- Table structure for student
    -- ----------------------------
    DROP TABLE IF EXISTS `student`;
    CREATE TABLE `student` (
      `Sno` int(11) NOT NULL,
      `Sname` varchar(255) CHARACTER SET utf8 DEFAULT NULL,
      `Ssex` varchar(255) CHARACTER SET utf8 DEFAULT NULL,
      `Sage` int(11) DEFAULT NULL,
      `Sdept` varchar(255) CHARACTER SET utf8 DEFAULT NULL,
      PRIMARY KEY (`Sno`)
    ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
    -- ----------------------------
    -- Records of student
    -- ----------------------------
    INSERT INTO `student` VALUES ('201215121', '刘晨', '女', '19', 'CS');
    INSERT INTO `student` VALUES ('201215122', '罗琪', '女', '17', 'CS');
    INSERT INTO `student` VALUES ('201215123', '刘中江', '男', '18', 'MA');
    INSERT INTO `student` VALUES ('201215125', '曹志雄', '男', '18', 'CS');
    INSERT INTO `student` VALUES ('201215126', '刘琰', '男', '19', 'CS');
    INSERT INTO `student` VALUES ('201215127', '刘言曌', '男', '19', 'CS');
    INSERT INTO `student` VALUES ('201215128', '曹志雄', '男', '19', 'CS');
    INSERT INTO `student` VALUES ('201215207', '曹阿瞒', '男', '19', 'IS');
    INSERT INTO `student` VALUES ('201215208', '春日风', '女', '18', null);

 
    #### SELECT 常用语句####
    #查询年龄在18-19的学生
    #select * from student where Sage between 18 and 19;
    #查询年龄不在18-19的学生
    #select * from student where Sage not between 18 and 19;
    #查询计算机科学系(CS系)，数学系(MA系)和信息系(IS)学生
    #select * from student where Sdept in('CS','MA','IS');
    #查询既不是计算机系(IS系)，也不是信息系(MA系)和信息系(IS系)学生
    #select * from student where Sdept not in('CS','MA','IS');
    #查询姓刘的学生
    #select * from student where Sname like '刘%';
    #查询姓欧阳，且全名为三个汉字的学生
    #select *from student where Sname like '欧阳_';
    #查询名字中第二个字为晨的学生
    #select * from student where Sname like '_晨';
    #查询不姓刘的学生
    #select * from student where Sname not like '刘%';
    #查询缺少成绩的学生的学号和相对的课程号
    #select sno,cno from sc where grade is null;
    #查询所有有成绩的学生的学号和课程号
    #select sno,cno from sc where grade is not null;
    #查询选修了3号课程的学生的学号，姓名和分数，按成绩降序排序
    #select sc.sno,student.sname,sc.grade from student,sc where cno=3 and student.sno=sc.sno order by grade desc;
    #查询全体学生，按所在系升序排序，同一个系按年龄降序
    #select * from student order by sdept asc,sage desc ;
    #查询学生总人数
    #select count(*) from student;
    #查询选修了课程的学生总人数
    #select count(distinct sno) from sc ;
    #计算3号课程的平均分
    #select avg(grade) from sc where cno=2;
    #查询学号201215121 选修课程的总分数
    #select sum(grade) from sc where sno='201215121';
    #查询每个学生及其选修课的情况
    #select * from student, sc where student.sno = sc.sno;
    #查询选修了2号课程且成绩在90分以上的所有学生
    #select * from sc where cno=2 and grade>90;
    #左外连接
    #select student.Sno,Sname,Ssex,Sage,Sdept,Cno,Grade from student left outer join sc on (student.sno = sc.sno);
    #多表连接
    #select student.sno,sname,cname,grade from student, sc, course where student.sno = sc.sno and course.cno = sc.cno
    #嵌套查询-查询选修了2号课程的学习姓名
    #select sname from student where sno in (select sno from sc where cno='2');
    #查询与刘晨在同一系学习的学生
    #select * from student where sdept = (select sdept from student where sname = '刘晨');
    #select * from student where sdept in (select sdept from student where sname = '刘晨');
    #select * from student s1,student s2 where s1.sdept = s2.sdept and s1.sname = '刘晨';
    #查询选修了信息系统的学生
    #select * from student,sc,course where sc.sno = student.sno and sc.cno = course.cno and course.cname = '信息系统'; ;
    #select * from student where sno in (select sno from sc where cno = ( select cno from course where cname  = '信息系统' ));
    #找出每个学生超过其选修平均成绩的课程号
    #select * from sc where grade > (select avg(grade) from sc where sno = sc.Sno);
    #查询非计算机科学系中比计算机科学系任意一个学生年龄小的学生
    #select * from student where sage < any (select sage from student) and sdept != 'cs';
    #select * from student where sage < (select max(sage) from student) and sdept != 'cs';
    #查询非计算机系中比计算机系所有年龄都要小的学生
    #select * from student where sage < all (select sage from student ) and sdept != 'cs';
    #select * from student where sage < (select min(sage) from student);
    #查询选修了2号课程的学生
    #select * from student where exists (select * from sc where cno = 2 and sc.sno = student.sno);
    #select * from student where sno in (select sno from sc where cno = 2);
    #查询没有选修2号课程的学生
    #select * from student where not exists (select * from sc where cno = 2 and sc.sno = student.sno);
    #select * from student where student.sno not in (select sc.sno from sc where sc.sno = 2);
    #查询选修了全部课程的学生
    -- select * from student where not exists 
    -- (
    --  select * from course where not exists  
    --  (
    --      select * from sc where sc.sno = student.sno and cno = course.cno
    --  )
    -- ) 
    -- select sno from 
    -- (
    --  select sno,count(*) as sum from sc group by sno  having sum = 
    --  (
    --      select count(*) from course
    --  )
    -- ) as A 
    # 集合查询 UNION (或，并集)
    #select * from student where Sname = '罗琪' UNION select * from student where Sname = '刘言曌';
    #select * from student where Sname = '罗琪' or Sname = '刘言曌';
    #找出每个学生超过自己选修课程平均成绩的课程号
    -- select * from sc,
    -- (
    --  select sno,avg(grade) as avg_grade from sc group by sno
    -- ) as A
    -- where A.sno = sc.sno and sc.grade > A.avg_grade;
    #### INSERT 常用语句 ####
    #将一个新学生插入到 Student 表中
    #insert into Student value(201215128, '曹志雄', '男', 20, 'MA');
    #insert into student(sno,sname,ssex,sage,sdept) values (201215207, '曹阿瞒','男',19, 'IS');
    #### UPDATE 常用语句 ####
    #修改某一个元组的值
    #将罗琪的年龄-1
    #update student set Sage = '18' where Sname = '罗琪'
    #修改多个元组的值
    #将所有的学生年龄-1
    #update Student set Sage = Sage - 1;
    #带子查询的修改语句
    #将计算机系的学生成绩+5
    -- update sc  
    -- set grade = grade + 5
    -- where sno in
    -- (select sno from student where sdept = 'CS');
    #### DELETE 常用语句 ####
    #先添加一条学生记录，然后删除他
    #insert into student value(201215130,'张三','男',19,'IS');
    #delete from student where sno = '201215130';
    #删除多条记录
    ##delete from sc;
    #### 空值的处理 ####
    #空值产生
    #添加一个学生，学院为NULL
    #insert into student value(201215208, '春日风','女',18,NULL);
    #将曹志雄的学院设置为NULL
    #update student set sdept = NULL where sname = '曹志雄';
    #空值判断
    #查询没有先行课的课程
    #select * from course where cpno is null;
    #查询有先行课的课程
    #select * from course where cpno is not null
    #### 视图常用语句 ####
    #创建一个男生视图
    -- create view is_boy 
    --  as 
    -- select * from student where ssex = '男';
    #查询视图
    #select * from is_boy where sage < 19
    #更新视图
    #update is_boy set sage = sage +1 where sname = '刘中江'
    #删除视图
    #drop view is_boy;

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