77. DBMS GATE Questions - Join Algorithm | Nested loop & Block Nested loop Join | Crack GATE CSE

Опубликовано: 01 Январь 1970
на канале: CRACK GATE CSE

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In this video we have discussed the previous year gate questions on Join Algorithms. This topic is very easy and also the questions are quite simple.
The questions discussed are:

GATE 2005 IT-82a:
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 Nested-loop join algorithm is employed to perform the join, with the most appropriate choice of table to be used in outer loop, the number of block accesses required for reading the data are
A. 800000 B. 40080 C. 32020 D.100
Answer: C is Right.

GATE 2005 IT-82b:
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
A. 0 B. 30400 C.38400 D.798400
Answer: B is Right.

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