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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?

https://gateoverflow.in/176728/relational-algebra

how ans is 2000

because there is noting specify about foreign key constraint ,then how we assume that r1.R is always a subset of r2.R  .

in Databases by (14 points) | 19 views
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But when comes to max, 2000 tuples is the only possible... To match this case, only option is, r1.R is subset to r2.R, right ?

 

Actually the question is not about no.of tuples, it's about testing commutative property of natural join

1 Answer

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ANSWER:FOR THIS OF QUESTION CHECK THE COMMON ATTRIBUTE THEREFORE IT WILL PRINT  ONLY 2000 TUPLES.

AND VICE VERSA YOU CAN CHECK

TAKE A SAMPLE TABLE EXAMPLE.
 

TABLE R1

P

Q

R

1

 

3

2

 

3

..

 

..

..

 

3

2000

 

3

 

 

TABLE R2

R

S

T

1

 

 

2

 

 

3

 

 

..

 

 

2500

 

 

 

 

by (112 points)
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