Gce Model Questions Vol1 2019 Computer Studies Question 34
Practice objective / multiple choice question 34 from the 2019 Gce Model Questions Vol1 Computer Studies examination.
A database table contains 1,200,000 rows. Column A is indexed and has a selectivity of 0.001 (i.e., about 0.1 % of rows match a given value). Column B is not indexed, and a condition on B selects roughly 5 % of the total rows. A query uses the index on A and then scans the resulting rows to test the B condition.\n\n(a) How many rows are examined (i.e., how many I/O operations are performed) using this plan?\n(b) If a composite index on (A, B) existed with a combined selectivity of 0.0002, how many rows would be examined with the composite index?
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This is Gce Model Questions Vol1 2019 Computer Studies Question 34. It is one of the objective questions from the 2019 Gce Model Questions Vol1 Computer Studies examination.
Difficulty level: Medium .
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