3 3 votes Consider the relations r1(P, Q, R) and r2(R, S, T) with primary keys P and R respectively. The relation r1 contains 2000 tuples and r2 contains 2500 tuples. The maximum size of the join r1⋈ r2 is equal to r2⋈ r1 true or false? Databases relational-calculus joins relations relational-algebra databases + – learner_geek 2.9k views answer comment Share Follow Print See all 5 Comments 5 5 Comments reply Shubhanshu commented Dec 3, 2017 reply Follow flag True: As Natural Join is a commutative operator. 1 1 replyShare learner_geek commented Dec 3, 2017 reply Follow flag Can you give small example 0 0 replyShare learner_geek commented Dec 3, 2017 reply Follow flag As I am getting r1⋈ r2 2000 and r2⋈ r1 2500 so please help me to correct my result 1 1 replyShare Shubhanshu commented Dec 3, 2017 reply Follow flag Refer this :- http://www.cs.sfu.ca/CourseCentral/354/zaiane/material/notes/Chapter12/node6.html 2 2 replyShare KUSHAGRA गुप्ता commented Nov 23, 2019 reply Follow flag $(\underline P,Q,\fbox{R})$ $( \fbox{$\underline R$},S,T)$ NK key Many : 1 $Ans: 2000$ 0 0 replyShare Please log in or register to add a comment.
Best answer 2 2 votes answer is 2000 r1 table P Q R 1 2 3 4 5 6 r2 table R S T 3 10 11 6 12 13 9 14 15 r1 natural join r2 P Q R S T 1 2 3 10 11 4 5 6 12 13 here natural join is commutative so number of rows will be 2000 from above example we drive as r1 table contain 2 rows and r2 table contain 3 rows but R attribute's (3 and 6) only matched. pranab ray answered Dec 3, 2017 • selected Dec 3, 2017 by learner_geek pranab ray comment Share Follow See all 4 Comments 4 4 Comments reply learner_geek commented Dec 3, 2017 i edited by learner_geek Dec 3, 2017 reply Follow flag Page1 0 0 replyShare learner_geek commented Dec 3, 2017 i reshown by learner_geek Dec 3, 2017 reply Follow flag Page 2 0 0 replyShare learner_geek commented Dec 3, 2017 i edited by learner_geek Dec 3, 2017 reply Follow flag Yes,we would get identical tuples in both cases so,answer 2000 is correct! 0 0 replyShare Himanshu Kumar Gupta commented Jul 28, 2020 reply Follow flag but there is noting specify about foreign key constraint ,then how we assume that r1.R is always a subset of r2.R ..please clearify 0 0 replyShare Please log in or register to add a comment.
