数据库管理系统概述英文版课件：7 revision

1、COMP231 RevisionPrepared by Raymond WongCOMP2311Revision1. ER DiagramPhase 1 and Phase 3ER-diagram, Relation and proof of the 3rd normal formE.g. Student takes a courseStudentStudent ID UniqueStudent NameCourseCourse ID UniqueCourse NameStudentStudent IDStudent NameCourseCourse IDCourse NameCOMP2312

2、Revision1. ER DiagramE.g. Student takes a courseStudentStudent IDStudent NameCourseCourse IDCourse NameTakeAssumption:Each student takes at least one courseEach course is taken by at least one studentSchemaStudentCourseTake(Student ID, Student Name)(Course ID, Course Name)(Student ID, Course ID)Phas

3、e 1 and Phase 3ER-diagram, Relation and proof of the 3rd normal formCOMP2313Revision1. ER DiagramE.g. Student takes a courseAssumption:Student ID is unique Student ID can uniquely identify a studentCourse ID is unique Course ID can uniquely identify a courseSchemaStudentCourseTake(Student ID, Studen

4、t Name)(Course ID, Course Name)(Student ID, Course ID)Non-trivial Functional DependencyStudent ID Student NameCourse ID Course NameCOMP2314Revision1. ER DiagramSchemaStudentCourseTake(Student ID, Student Name)(Course ID, Course Name)(Student ID, Course ID)Non-trivial Functional DependencyStudent ID

5、Student NameCourse ID Course NameProof of 3NFR is in 3NF if for any A in F A is trivial (A ), or contains a key for R, orA is part of some key(s) for RSchema Student is in 3NFBecausefor Student ID Student Name,Student ID is a key of StudentSchema Course is in 3NFBecausefor Course ID Course Name,Cour

6、se ID is a key of CourseSchema Take is in 3NFBecauseany functional dependencies for Relation Take are trivial.COMP2315Revision2. Relational Algebra/SQLQuery 1: Find the name of all students who take the course taught by “Prof. Wong” studentcoursetakesidsnamecidnamecnameteacherstudent (sid, sname)cou

7、rse (cid, cname, teacher)take (sid, cid)Query 2: Find the name of all students who take ALL courses taught by “Prof. Wong” COMP2316Revision2. Relational Algebra/SQLQuery 1: Find the name of all students who take the course taught by “Prof. Wong” studentcoursetakesidsnamecidnamecnameteacherstudent (s

8、id, sname)course (cid, cname, teacher)take (sid, cid)select S.snamefrom student S, take T, course Cwhere S.sid = T.sid and T.cid = C.cid and C.teacher = Prof. Wongsname ( )teacher=Prof. Wong(course)student takeCourses taught by Prof. WongStudents who take courses taught by Prof. WongRelationalAlgebr

9、aSQLCOMP2317Revision2. Relational Algebra/SQLQuery 2: Find the name of all students who take ALL courses taught by “Prof. Wong” studentcoursetakesidsnamecidnamecnameteacherstudent (sid, sname)course (cid, cname, teacher)take (sid, cid)snameteacher=Prof. Wong(course)(student )Courses taught by Prof.

10、WongA set of cid of courses taught by Prof. WongRelationalAlgebracid ( )set_of_cid A set of sid (of students) who take all courses taught by Prof. Wong(take / set_of cid)Get back snameresult COMP2318Revision2. Relational Algebra/SQLstudentcoursetakesidsnamecidnamecnameteachere.g.1 231537Prof. Wong t

11、eaches 231251252271Peter takesPeter takes only ONE course taught by Prof. Wong Peter DOES NOT take ALL courses taught by Prof. Wong 231537Prof. Wong teaches 231251252271Raymond takes537Raymond takes TWO courses taught by Prof. Wong Raymond TAKES ALL courses taught by Prof. Wong e.g.2COMP2319Revision

12、2. Relational Algebra/SQLe.g.1 231537Prof. Wong teaches 231251252271Peter takesPeter DOES NOT take ALL courses taught by Prof. Wong 231537Prof. Wong teaches 231251252271Raymond takes537Raymond TAKES ALL courses taught by Prof. Wong e.g.2=537Exist?Yes=Exist?NoConclusionA set of courses taught by Prof

13、. WongA set of courses taken by RaymondCourses taughtby Prof. WongCourses takenby a student=Resultif exist = yes, the student DOES NOT take ALL courses taught by Prof. WongIf exist = no, the student takes ALL courses taught by Prof. Wong COMP23110Revision2. Relational Algebra/SQLConclusionCourses ta

14、ughtby Prof. WongCourses takenby a student=ResultQuery 2: Find the name of all students who take ALL courses taught by “Prof. Wong” if exist = yes, the student DOES NOT take ALL courses taught by Prof. WongIf exist = no, the student takes ALL courses taught by Prof. Wong calculateCourses taughtby Pr

15、of. WongCourses takenby student S=ResultFor each student S,If exist = no, the student takes ALL courses taught by Prof. Wong (i.e “not exists” in SQL)COMP23111Revision Query 2: Find the name of all students who take ALL courses taught by “Prof. Wong” calculateCourses taughtby Prof. WongCourses taken

16、by student S=ResultFor each student S,If exist = no, the student takes ALL courses taught by Prof. Wong (i.e “not exists” in SQL)select S.snamefrom student Swhere not existsstudent (sid, sname)course (cid, cname, teacher)take (sid, cid)( select C.cid from course C where teacher = Prof. Wong) ( selec

17、t T.cid from take T where T.sid = S.sid)Courses taught by Prof. Wong Courses taken by student S ( except )SQLCOMP23112RevisionQuery 1: Find the name of all students who take the course taught by “Prof. Wong” select S.snamefrom student S, take T, course Cwhere S.sid = T.sid and T.cid = C.cid and C.te

18、acher = Prof. Wongsname ( )teacher=Prof. Wong(course)student takeRelationalAlgebraSQLQuery 2: Find the name of all students who take ALL courses taught by “Prof. Wong” snameteacher=Prof. Wong(course)(student )cid ( )set_of_cid (take / set_of cid)result RelationalAlgebraSQLselect S.snamefrom student

19、Swhere not exists( select C.cid from course C where teacher = Prof. Wong) ( select T.cid from take T where T.sid = S.sid) ( except )One of the courses taught by Prof. WongAll courses taught by Prof. WongNatural JoinNatural JoinDivisionNot exists(Except)COMP23113Revision2. Relational Algebra/SQLQuery

20、 3: Find the cid of all courses of class size 10studentcoursetakesidsnamecidnamecnameteacherstudent (sid, sname)course (cid, cname, teacher)take (sid, cid)Query 4: Find the cid and cname of all courses of class size 10COMP23114Revision2. Relational Algebra/SQLQuery 3: Find the cid of all courses of class size 10studentcoursetakesidsnamecidnamecnameteacherstudent (sid, sname)course (cid, cname, teacher)take (sid, cid)select T.cidfrom take Tgroup by T.