mysql在查询时卡住了

我有一个大学的数据库。我被卡住了，不明白我必须写的一个问题。我必须检索教授计算机科学课程的教员的姓名、他们所教授的课程、课程编号、课程编号、年份和学期，以及这些课程的学生总数。 我不确定输出应该是什么样的。 到目前为止，我写了：

SELECT i.name,t.number,t.year,t.semester,t.section_number FROM Instructor as i,Teaches as t WHERE i.department LIKE '%Computer Science%'; 

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);

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您需要了解SQL中的

JOIN

子句

您可能还会发现这是一个有用的工具

下面是一个示例查询

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您看到了如何使用各个表中的各种id号将记录从一个表附加到下一个表吗？

请阅读SQL JOIN。您需要将多个表连接在一起才能得到答案。请注意，

SELECT

statements.codinghorror.com/blog/2007/10/a-visual-explainion-of-sql-joins.htmlSELECT DISTINCT i.name、t.number、t.year、t.term、t.section\u number、COUNT（c.student\u id）中也允许换行作为TotalStudents，来自讲师as i加入讲师as t使用（讲师id）加入以c注册，其中i.系如“%Computer Science%”和c.number=t.number；

SELECT i.name,t.number,
       c.title,
       t.year,t.semester,t.section_number 
  FROM Instructor as i
  JOIN Teaches as t USING(instructor_id)
  JOIN Course as c USING(number)
 WHERE i.department LIKE '%Computer Science%';