–1 votes –1 votes PLEASE EXPLAIN WHEATHER IT WOULD BE SOME EC DEPARMENT OR ALL EC DEPARTMENT I THINK ALL BECOZ IT IS SELECTION EID OF STUDENT WHO HAVE NOT ENROLLED IN ANY COURSE OF EC Databases databases relational-algebra made-easy-test-series + – Himanshu Kashyap asked Jan 12, 2019 edited Mar 4, 2019 by ajaysoni1924 Himanshu Kashyap 653 views answer comment Share Follow See all 6 Comments See all 6 6 Comments reply Utkarsh Kumar Raut commented Jan 12, 2019 reply Follow Share As I tried to understand the query, it targets students those who are enrolled into courses offered by CS department but are not taking any courses which EC department offering. Hence making is option (D) As this query first filter out all students who took EC department courses, later minus it from all students who took CS department courses. Concluding — List of SID of Students who took CS Department Course but not any courses offered by EC! Let me know your thoughts. 0 votes 0 votes Himanshu Kashyap commented Jan 12, 2019 reply Follow Share bro i am also thinking this but given A ,i am thinking they had given it wrong 0 votes 0 votes Ayush Upadhyaya commented Jan 12, 2019 reply Follow Share It's correct. The equivalent operation is $A-B \equiv A \cap \lnot B$ Now make corresponding english statement of the SQL and it would be same as above. That was another technique I told. Now even if there exists a student who has say taken only 1 cs course and only 1 ec course out of say total 5 ec courses, then also, this student won't be represented in result set. In short it is selecting those students who have taken cs but not ec courses. 1 votes 1 votes Himanshu Kashyap commented Jan 12, 2019 reply Follow Share How A is correct it is saying some of the course of the Ec which means it will the output if some student have taken some ec and some not ec It should be like which dont have taken all the Ec course Please correct me i am confuse with some and all 0 votes 0 votes jatin khachane 1 commented Jan 12, 2019 reply Follow Share @Ayush Upadhyaya its D then ? 0 votes 0 votes Ayush Upadhyaya commented Jan 12, 2019 reply Follow Share Consider four classes of students Class A-Who take only CS courses and no student here has taken even a single EC course. Class B-WHo Take only EC courses Class C-Who take Some Cs course and Some EC course both at same time. Class D-Who have taken some cs courses and all ec courses. Final result set will include only students from class A. 1 votes 1 votes Please log in or register to add a comment.