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Consider the following relation R(XYZ) with X as the primary key and Z as the foreign key referencing X with a delete cascade.

X1 Y1 X7
X3 Y1 X2
X5 Y4 X3
X2 Y2 X1
X9 Y5 X3
X7 Y3 X8
X4 Y2 X2

 Suppose tuple (X2, Y2, X1) is deleted, as a result what will be the number of tuples in R after deletion?

in Databases 15 points 16 views
@shubhajit panday

Ans - 2

1 Answer

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As a result of deletion ( X2 Y2 X1) –  (X3 Y1 X2 ) , ( X4 Y2 X2 )  will be deleted.

As a result of deletion (X3 Y1 X2 )- (X5 Y4 X3 ) , ( X9 Y5 X3 ) will be deleted .

As a result of deletion ( X4 Y2 X2 ) – No tuples 

As a result of deletion ( X5 Y4 X3 ) – No tuples

As a result of deletion (  X9 Y5 X3 ) - No tuples


Ans will be 4 . 

PS –  since Z is referencing X , X8 must be present in X 

11 points