Self doubt

Question

Minimum number of tuples in R Natural join S where R and S contains m  and n tuples respectively .

Comments

@Shubhgupta it can also be 0 when there are no common values in the common attribute between the relations.

Can't it be the case ?

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answer will be $0$

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@Shobhit Joshi, yes I missed that case. Thanks!

Answer 1

The minimum number of tuples in $R$ Natural join $S$ is $zero,$ when both relations have a common attribute, but does not satisfy the condition.

Let us say

$R$

a	b
1	2
2	3

$S$

b	c
4	5
6	7

$R\Join_{<b=b>} S$

a	b	c

Number of tuples $=0$

And if both relation does not have any common attribute then natural join works as a cartessian product(or cross product).

$R$

a	b
1	2
2	3

$S$

c	d
4	5
6	7

$R$ Natural Join $S$

a	b	c	d
1	2	4	5
1	2	6	7
2	3	4	5
2	3	6	7

Number of tuples $=4$

Comments

@Shadan Karim

thanks

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@Lakshman Patel RJIT

if you add the answer, then questioner automatically notified....

no need to add separate comment !

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Ok Brother