Suppose a sequential file contains 50,000 records, and 5 milliseconds
are required to interrogate an entry. How long should we expect to wait
when retrieving a record from the middle of the file?(CAN YOU EXPLAIN
THE SOLUTION)
In terms of the relations shown below, what is the appearance of the
relation RESULT after executing each of these instructions: (you may
want to look at this question in the book to make sure you understand
the tables)
X relation                           Y
relation
U Â Â V Â Â WÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â R
  S
A Â Â Z Â Â 5Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 3
  J
B Â Â D Â Â 3Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 4
  K
C Â Â Q Â Â 5
a. RESULT <- PROJECT W from X
b. RESULT <- SELECT from X
               where W = 5
c. RESULT <- PROJECT S from Y
d. RESULT <- JOIN X and Y
               where X.W >= Y.R
Computer Science Homework Solutions
#95096
Database
Suppose a sequential file contains 50,000 records, and 5 milliseconds are required to interrogate an entry. How long should we expect to wait when retrieving a record from the middle of the file?(CAN YOU EXPLAIN THE SOLUTION)
In terms of the relations shown below, what is the appearance of the relation RESULT after executing each of these instructions: (you may want to look at this question in the book to make sure you understand the tables)
X relation Y relation
U V W R S
A Z 5 3 J
B D 3 4 K
C Q 5
a. RESULT <- PROJECT W from X
b. RESULT <- SELECT from X
where W = 5
c. RESULT <- PROJECT S from Y
d. RESULT <- JOIN X and Y
where X.W >= Y.R
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