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asked in Databases by Boss (6k points)   | 81 views

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Lets take an example, Below are three instances of table with ratio of tuples equal to the original relation.

A B C
 Y  Y  L
 P  Q  M
 C  D  N
 X  Z  O

 

C D E
 L  Z  A
 M  Z  A
 N  Z  A
 L  Z  B
 M  Z  B
 O  Z  B

 

E F
 A  Z
 B  Z

If we join tem in any way the resulting table will have 6 tuples 
We can thus conclude that P join Q join R will result in 300 tuples.

A B C D E F
 Y  Y  L  Z  A  Z
 Y  Y  L  Z  B  Z
 P  Q  M  Z  A  Z
 P  Q  M  Z  B  Z
 C  D  N  Z  A  Z
 X  Z  O  Z  B  Z

 

answered by Active (2.2k points)  
selected by
NO...if we join Q(CE) and R(E) then we can get 300 tuples.

Then with P....300 should be answer.
Suppose CE attributes have tuples as:

ab

ac

bb

bc

And EF attributes have tuples as:

bg

ct

Then the join of these results in tuples

abg

act

bct

bbg

Here we're getting the tuples from relation having maximum tuples. Correct me if I'm wrong @Rakesh
Thanks guys for correcting me, updated the answer with an example.
All credits to vaishali :)

Ths is wrongly framed question. They havent stated maximum or minimum.

If minumum, then its 0.

If maximum, then 300 tuples

^ how min = 0 ??

If one of C or E for all touple of relation Q is null ??
Consider the tables here:

 

               Table P

-------------------------------------------------

A          B       C

------------------------------------------------

1         1         1

2         2         2

.

.

200    200      200

 

          Table Q

------------------------------------

C            D              E

-------------------------------------

201         201            201

202         202            202

.

.

500         500            500

 

 

              Table R

------------------------------------------------

E                    F

------------------------------------------------

501              501

502              502

.

.

600              600
..........
@Vijay. I dont think that for relation Q, one of C or E can be null.
I thought, C in Q is foreign key pointng to C in P and similarly E in Q referring to E in R.

So, we should not consider foreign key even if there is common attribute between two relation unless it is mentioned explicitly. ??
@Vijay. Yes. We shouldn't consider unless explicitly stated because we have satisfied the conditions they have given.
But, if options are given, we need to consider that C is foreign key in Q   :P
....
maximum tupples can be 200.


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