Sample Questions and Answers
Printed From: One Stop GATE
Category: GATE AT A GLANCE
Forum Name: Other Discussions on GATE
Forum Discription: If you want to discuss some aspects of GATE which are not covered by any of the threads above, you are free to use this forum for those discussions.
URL: http://forum.onestopgate.com/forum_posts.asp?TID=980
Printed Date: 11Feb2025 at 2:58am
Topic: Sample Questions and Answers
Posted By: papri
Subject: Sample Questions and Answers
Date Posted: 05Apr2007 at 12:27am
Q.3. Databases
Consider three tables with following number of tuples in
each
S(a,b,c) = 100
R(a,d,e) = 80
T(x,d,f) = 90
Tuples in S and R with same value of attribute "a" = 60
Tuples in R and T with same value of attribute "d" = 70
Maximum and minimum number of tuples in
(S left outer join R) full outer join T is:
Options
1. 130 120
2. 150 140
3. 140 130
4. 140 120
Ans: 3
Explanation:
Consider, X = ( S left outer join R )
This will have 100 rows, with d = null for
40(100-60) rows.
X full outer join T: Here, the common values of d in
tables X and T can be between 50 and 60.
Case 1: Minimum value of common values of d between
X and T
Out of 80 values of d in R, 20 were not found in X (since X
has only 60 non-null values of d). These 20 can all be the ones
that were common between S and T. In this case the
common values between X and T will be 50.
Case 2: Maximum value of common values of d between X and T
Now assume that 20 values of d that were lost, none was common
between S and T. But this is not possible, because S has 80 tuples
and 70 values are common with T. So at least 10 common values will
get lost. Thus max. value of common d's will b 60.
Now full outer join (X + T - common values of d in X and T)
will be either
100 + 90 - 50 or 100 + 90 - 60.
Thus the answer is 140,130. Hence 3
|
|