EBK DATABASE SYSTEM CONCEPTS
7th Edition
ISBN: 9781260049268
Author: SILBERSCHATZ
Publisher: MCG COURSE
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Expert Solution & Answer
Chapter 15, Problem 8PE
Explanation of Solution
Sort-based
Suppose be two relations and has to be computed.
- Sort relation “s” on “S” for sort-based algorithm. Sort relation “r” on (T, S).
- Now, start scanning “r” and look at the “T” attribute values of the first tuple.
- Scan “r” till tuples have same value of “T”. Also scan “s” simultaneously and check whether every tuple of “s” also occurs as the “S” attribute of “r”, in a fashion similar to merge join.
- If this is the case, output that value of “T” and proceed with the next value of “T”.
- Relation “s” may have to be scanned multiple times but “r” will only be scanned once.
- Total disk accesses, after sorting both the relations, will be “|r| 9 N * |s|”, where “N” is the number of distinct values of “T” in “r”.
Hash-based algorithm for computing the relational division operation:
- Let assume that for any value of “T”, all tuples in “r” with that “T” value fit in memory, and consider the general case at the end...
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Chapter 15 Solutions
EBK DATABASE SYSTEM CONCEPTS
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