Hi, Making sure I\'m doing this right: Students(sid:decimal(9,0),sname:char(20),

Question

Hi,

Making sure I'm doing this right:

      Students(sid:decimal(9,0),sname:char(20), rno:int, major:char(20))

      Courses(cid:decimal(9,0),cname:char(20), fid:decimal(9,0), color:char(10), room:char(4))

      Enrolled(sid:decimal(9,0),cid:decimal(9,0))

      Faculty(fid:decimal(9,0),fname:char(20))    
Select the names of courses that do not have a studentcalled ‘Copycat’ enrolled in them.     
        PROJECTcname (( SELECTcources.cid ( CoursesJOIN Enrolled ) ] JOIN STUDENTS (SELECTsname !='Copycat' ( Students JOIN Enrolled)))

I'm pretty sure this is right, if this was sql I would use the -operator which might simply things.

      Students(sid:decimal(9,0),sname:char(20), rno:int, major:char(20))

      Courses(cid:decimal(9,0),cname:char(20), fid:decimal(9,0), color:char(10), room:char(4))

      Enrolled(sid:decimal(9,0),cid:decimal(9,0))

      Faculty(fid:decimal(9,0),fname:char(20))    
Select the names of courses that do not have a studentcalled ‘Copycat’ enrolled in them.     
        PROJECTcname (( SELECTcources.cid ( CoursesJOIN Enrolled ) ] JOIN STUDENTS (SELECTsname !='Copycat' ( Students JOIN Enrolled)))

I'm pretty sure this is right, if this was sql I would use the -operator which might simply things.

Explanation / Answer

   Dear,       Given relations are,       Students(sid:decimal(9,0),sname:char(20), rno:int, major:char(20))

      Courses(cid:decimal(9,0),cname:char(20), fid:decimal(9,0), color:char(10), room:char(4))

      Enrolled(sid:decimal(9,0),cid:decimal(9,0))

      Faculty(fid:decimal(9,0),fname:char(20))       Select the names ofcourses that do not have a student called ‘Copycat’enrolled in them.       SQL Query:          selectcname from Cources where cid in(          selectcid from Enrolled where sid in(          selectsid from Students where sname!='Copycat'));          selectcname from Cources where cid in(          selectcid from Enrolled where sid in(          selectsid from Students where sname!='Copycat'));
     Query in RELATIONALALGEBRA :          PROJECTcname([ SELECTcources.cid = enrolled.cid ( Cources X Enrolled) ] JOINenrolled.sid = students.sid[SELECTsname!='Copycat'( Students X Enrolled)])          Here, weare displaying cource names first by making cartesian product ofcources and enrollment with a common field "cid". Next we arejoining the the student and entolled relations with a common field"sid" and retrieving the student names not equal to"Copycat".        " I hope this will help you"

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