retagged by
472 views
0 votes
0 votes
Two queries equivalent to each other are specified for a relation R(A, B, C, D, E, F).

The queries are: • πA,B,C(σB>500(R))

• σB>500(πA,B,C(R))

The system maintains a B+ tree index for (A, B, C) on R. However, the index is unclustered. The relation R occupies 100 pages and the index structure needs 5 pages only. Compute the number of disk accesses required for each of the queries and thereby decide which one of the two queries will be preferred by the query optimizer for minimum cost of execution. The cost of query execution is primarily dependent on the number of disk accesses.
retagged by

Please log in or register to answer this question.

Related questions

0 votes
0 votes
0 answers
2
1 votes
1 votes
2 answers
4
kauray asked Apr 19, 2017
829 views
Write the smallest real number greater than 6.25 that can be represented in the IEEE-754 single precision format (32-bit word with 1 sign bit and 8-bit exponent).