INFO20003 Database Systems
Dr Farhana Q&A
INFO20003 Database Systems
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• Assignment 2 done and dusted • Peerwise is on!
• Best to start early to increase your ranking
• 3 bonus marks are well worth the effort
• Assignment 3 in Week 11
• It will be a quiz (but longer than weekly ones)
• Practice for our final exam (the long quiz as well)
• I will survey you soon on the preferred day
INFO20003 Database Systems 2
Quiz 7 walkthrough
• On the LMS…
INFO20003 Database Systems 3
Given: Reserves (R): NTuples(R) = 100, Nkeys(sid) =100,
Sailors (S): NTuples(S) =1000, Nkeys(rating) = 10 interval [1-10], age interval [0-100], Nkeys(sid)=1000
SELECT * FROM Sailors as S INNER JOIN Reserves as R ON S.SID = R.SID WHERE rating =8 and 20< age < 30;
Calculate result size:
NTuples(S) = 1000
NTuples(R) = 100
RF(S.SID=R.SID) = ?
RF(rating) = ?
RF(20