Operating-Systems
August 17, 2024Database-Management-System
Question 23 |
A database table T1 has 2000 records and occupies 80 disk blocks. Another table T2 has 400 records and occupies 20 disk blocks. These two tables have to be joined as per a specified join condition that needs to be evaluated for every pair of records from these two tables. The memory buffer space available can hold exactly one block of records for T1 and one block of records for T2 simultaneously at any point in time. No index is available on either table.
If, instead of Nested-loop join, Block nested-loop join is used, again with the most appropriate choice of table in the outer loop, the reduction in number of block accesses required for reading the data will be
0 | |
30400 | |
38400 | |
798400 |
Question 23 Explanation:
In Nested loop join the no. of block access will be,
400×80+20
= 32020 (calculated in previous question)
In block Nested loop join, the no. of block access will be
20×80+20 = 1620
∴ The difference is = 32020 – 1620 = 30400
400×80+20
= 32020 (calculated in previous question)
In block Nested loop join, the no. of block access will be
20×80+20 = 1620
∴ The difference is = 32020 – 1620 = 30400
Correct Answer: B
Question 23 Explanation:
In Nested loop join the no. of block access will be,
400×80+20
= 32020 (calculated in previous question)
In block Nested loop join, the no. of block access will be
20×80+20 = 1620
∴ The difference is = 32020 – 1620 = 30400
400×80+20
= 32020 (calculated in previous question)
In block Nested loop join, the no. of block access will be
20×80+20 = 1620
∴ The difference is = 32020 – 1620 = 30400
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