MySQL似乎无法正常工作

Question

我有这个大学数据库，我必须找回教授计算机科学课程的教师的名字，他们正在教授的部分（课程编号，部门编号，年份，学期）以及部分中的学生总数

到目前为止，这是管理但输出不正确的原因。

SELECT  i.instructor_id,o.year,o.semester,o.section_number, o.number as CourseNumber,o.Total_num_student
FROM Instructor i JOIN
(SELECT t.instructor_id,t.year,t.semester,t.section_number,o1.number,o1.Total_num_student
 FROM teaches t JOIN
 (SELECT COUNT(s.student_id) as Total_num_student,e.section_number,e.number 
  FROM Student s JOIN
  enrolls e
  ON s.student_id=e.student_id
  GROUP BY section_number,e.number) as o1
 ON o1.section_number=t.section_number) as o
on i.instructor_id=o.instructor_id
WHERE department='Computer Science';

你能看出输出有什么问题。

create table Course (
  number int,
  title varchar(255),
  credits int,
  syllabus varchar(255),
PRIMARY KEY (number)
  );
INSERT INTO Course VALUES (620,'Algorithm',3,'XYZ');
INSERT INTO Course VALUES (621,'Algorithm',3,'XYZ');
INSERT INTO Course VALUES (232,'Java',2,'ABC');
INSERT INTO Course VALUES (420,'Cpp',2,'PQRS');
INSERT INTO Course VALUES (720,'Big Data',3,'NVGY');
INSERT INTO Course VALUES (120,'Intelligent System',4,'KJHU');
INSERT INTO Course VALUES (220,'Operating System',3,'GED');
INSERT INTO Course VALUES (480,'Graphics',4,'RSFN');
INSERT INTO Course VALUES (520,'Distributed Networks',3,'NHU');
INSERT INTO Course VALUES (820,'Data Mining',3,'TYU');
INSERT INTO Course VALUES (700,'Cryptography',1,'MNO');

create table Student (
  student_id int,
  name varchar(255),
  department varchar(255),
  PRIMARY KEY (student_id)
  );

INSERT INTO Student VALUES (2345,'Mike','Computer Science');
INSERT INTO Student VALUES (346,'Rob','Computer Science');
INSERT INTO Student VALUES (789,'Nick','Game Design');
INSERT INTO Student VALUES (675,'Sara','Computer Science');
INSERT INTO Student VALUES (123,'Raj','Chemical');
INSERT INTO Student VALUES (5331,'Jack','Biotech');
INSERT INTO Student VALUES (1023,'Michelle','Chemical');
INSERT INTO Student VALUES (9800,'Jie','Game Design');
INSERT INTO Student VALUES (7834,'Dan','Petroleum');
INSERT INTO Student VALUES (4567,'Patrick','Computer Science');


create table Instructor (
  instructor_id int,
  name varchar(255),
  department varchar(255),
  title varchar(255),
  PRIMARY KEY (instructor_id)
  );


INSERT INTO Instructor VALUES (12,'John','Computer Science','Java');
INSERT INTO Instructor VALUES (23,'Bischof','Mechanical','Drawing');
INSERT INTO Instructor VALUES (56,'Kwon','Biotech','Biology');
INSERT INTO Instructor VALUES (78,'Deever','Security','Cryptography');
INSERT INTO Instructor VALUES (45,'Jin','Computer Science','Cpp');
INSERT INTO Instructor VALUES (67,'Bailey','Petroleum','Metalurgy');
INSERT INTO Instructor VALUES (90,'Richard','Industrial','Manufacture');
INSERT INTO Instructor VALUES (11,'Joe','Chemical','Chemistry');
INSERT INTO Instructor VALUES (24,'Roger','Game Design','Cpp');
INSERT INTO Instructor VALUES (55,'Zack','Computer Science','Design');


create table CourseOffering (
  number int,
  year int,
  semester int,
  section_number int,
  classroom int,
  PRIMARY KEY (number,year,semester,section_number),
  FOREIGN KEY (number) REFERENCES Course (number)
  );

INSERT INTO CourseOffering VALUES (620,2012,2,102,3540);
INSERT INTO CourseOffering VALUES (621,2013,3,103,3545);
INSERT INTO CourseOffering VALUES (232,2011,1,103,3455);
INSERT INTO CourseOffering VALUES (420,2013,3,101,2650);
INSERT INTO CourseOffering VALUES (720,2013,3,100,3455);
INSERT INTO CourseOffering VALUES (120,2014,1,102,3000);
INSERT INTO CourseOffering VALUES (220,2008,2,104,1450);
INSERT INTO CourseOffering VALUES (480,2009,4,106,1400);
INSERT INTO CourseOffering VALUES (520,2010,3,102,3500);
INSERT INTO CourseOffering VALUES (820,2008,3,100,2700);
INSERT INTO CourseOffering VALUES (700,2012,1,103,2540);

create table CourseOffering_Timing (
  number int,
  year int,
  semester int,
  section_number int,
  timing int,
  PRIMARY KEY (number,year,semester,section_number,timing),
  FOREIGN KEY (number) REFERENCES Course (number)
  );

INSERT INTO CourseOffering_Timing VALUES (620,2012,2,102,9);
INSERT INTO CourseOffering_Timing VALUES (621,2013,3,103,9);
INSERT INTO CourseOffering_Timing VALUES (232,2011,1,103,3);
INSERT INTO CourseOffering_Timing VALUES (420,2013,3,101,2);
INSERT INTO CourseOffering_Timing VALUES (720,2013,3,100,5);
INSERT INTO CourseOffering_Timing VALUES (120,2014,1,102,4);
INSERT INTO CourseOffering_Timing VALUES (220,2008,2,104,10);
INSERT INTO CourseOffering_Timing VALUES (480,2009,4,106,12);
INSERT INTO CourseOffering_Timing VALUES (520,2010,3,102,4);
INSERT INTO CourseOffering_Timing VALUES (820,2008,3,100,2);
INSERT INTO CourseOffering_Timing VALUES (700,2012,1,103,3);

create table PreRequisite (
  number int,
  prerequisite_number int,
  PRIMARY KEY (number,prerequisite_number),
  FOREIGN KEY (number) REFERENCES Course(number)
  );

INSERT INTO PreRequisite VALUES (620,480);
INSERT INTO PreRequisite VALUES (621,481);
INSERT INTO PreRequisite VALUES (232,120);
INSERT INTO PreRequisite VALUES (420,320);
INSERT INTO PreRequisite VALUES (720,580);
INSERT INTO PreRequisite VALUES (120,110);
INSERT INTO PreRequisite VALUES (220,130);
INSERT INTO PreRequisite VALUES (480,380);
INSERT INTO PreRequisite VALUES (520,360);
INSERT INTO PreRequisite VALUES (820,700);
INSERT INTO PreRequisite VALUES (700,610);


create table enrolls (
  student_id int,
  number int,
  year int,
  semester int,
  section_number int,
  grade varchar(10),
  PRIMARY KEY (student_id,number,year,semester,section_number),
  FOREIGN KEY (number,year,semester,section_number) REFERENCES CourseOffering(number,year,semester,section_number),
  FOREIGN KEY (student_id) REFERENCES Student (student_id)  
  );

INSERT INTO enrolls VALUES (2345,620,2012,2,102,'A');
INSERT INTO enrolls VALUES (346,232,2011,1,103,'B');
INSERT INTO enrolls VALUES (789,420,2013,3,101,'A');
INSERT INTO enrolls VALUES (675,621,2013,3,103,'C');
INSERT INTO enrolls VALUES (123,120,2014,1,102,'B');
INSERT INTO enrolls VALUES (5331,220,2008,2,104,'A');
INSERT INTO enrolls VALUES (1023,480,2009,4,106,'B');
INSERT INTO enrolls VALUES (9800,520,2010,3,102,'A');
INSERT INTO enrolls VALUES (7834,820,2008,3,100,'C');
INSERT INTO enrolls VALUES (4567,700,2012,1,103,'F');

create table teaches (
  instructor_id int,
  number int,
  year int,
  semester int,
  section_number int,
  PRIMARY KEY (instructor_id, number, year, semester, section_number),
  FOREIGN KEY (instructor_id) REFERENCES Instructor(instructor_id),
  FOREIGN KEY ( number, year, semester, section_number) REFERENCES CourseOffering( number, year, semester, section_number)
  );



INSERT INTO teaches VALUES (12,620,2012,2,102);
INSERT INTO teaches VALUES (12,621,2013,3,103);
INSERT INTO teaches VALUES (23,232,2011,1,103);
INSERT INTO teaches VALUES (56,420,2013,3,101);
INSERT INTO teaches VALUES (78,720,2013,3,100);
INSERT INTO teaches VALUES (45,120,2014,1,102);
INSERT INTO teaches VALUES (67,220,2008,2,104);
INSERT INTO teaches VALUES (90,480,2009,4,106);
INSERT INTO teaches VALUES (11,520,2010,3,102);
INSERT INTO teaches VALUES (24,820,2008,3,100);
INSERT INTO teaches VALUES (55,700,2012,1,103);

Answer 1

看看这是否适合你

SELECT Instructor.name AS instructor_name, teaches.section_number AS section_number,
 teaches.year AS year, teaches.semester AS semester, COUNT(enrolls.student_id) FROM Instructor
 INNER JOIN teaches ON teaches.instructor_id = Instructor.instructor_id 
 INNER JOIN enrolls ON teaches.section_number = enrolls.section_number AND teaches.semester = enrolls.semester AND teaches.year = enrolls.year
 WHERE department='Computer Science' 
 GROUP BY Instructor.name, teaches.section_number, teaches.year, teaches.semester;

Answer 2

我不完全确定你想要实现的目标但是如果你想保留部分信息，那就是：

SELECT a.instructor_id, group_concat(DISTINCT a.year SEPARATOR ', ') YEAR, group_concat(DISTINCT a.semester SEPARATOR ', ') SEMESTER, group_concat(DISTINCT a.section_number SEPARATOR ', ') SECTION_NUMBER, group_concat(DISTINCT a.coursenumber SEPARATOR ', ') COURSENUMBER, count(a.student_id) as Total_num_student FROM (
SELECT e.student_id, i.instructor_id, t.year,t.semester,t.section_number, t.number as CourseNumber  
FROM instructor i
JOIN teaches t
ON i.instructor_id = t.instructor_id
JOIN enrolls e
ON e.section_number=t.section_number
WHERE department='Computer Science') a
GROUP BY a.instructor_id
;


SELECT a.instructor_id,  a.year, a.semester, a.section_number, a.coursenumber, count(a.student_id) as Total_num_student FROM (
SELECT e.student_id, i.instructor_id, t.year,t.semester,t.section_number, t.number as CourseNumber  
FROM instructor i
JOIN teaches t
ON i.instructor_id = t.instructor_id
JOIN enrolls e
ON e.section_number=t.section_number
WHERE department='Computer Science') a
GROUP BY a.instructor_id, a.section_number
;

SQLFiddle demo