Consider the following statistics for the following relations Employee...
Given,
Here, every employee block has to transfer projects to a maximum of 40 transfers and every tuple of employees to projects tuples so a maximum of 2000 × 20.
The number of block transfers in the Natural Join of two relations in the worst-case is
= et + pt × eb.
= 40 + 2000 × 20
=40040
Hence, the correct option is (A).
Consider the following statistics for the following relations Employee...
Number of block transfers in Natural Join:
The number of block transfers in the worst case for the Natural Join of two relations can be calculated using the following formula:
Number of block transfers = (Number of blocks in the first relation) + (Number of blocks in the second relation) - (Number of common blocks)
In this case, the number of blocks in the Employee relation (BEmp) is 20 and the number of blocks in the Projects relation (BPrj) is 40. To find the number of common blocks, we need to consider the common attribute between the two relations. Let's assume that the common attribute is "EmployeeID".
The number of distinct EmployeeIDs in the Employee relation (NEmp) is given as 1000. Since each block can hold multiple tuples, the number of blocks required to store the Employee relation can be calculated as:
Number of blocks for Employee relation = ceil(NEmp / tuples_per_block)
Assuming that each block can hold 100 tuples, the number of blocks for the Employee relation can be calculated as:
Number of blocks for Employee relation = ceil(1000 / 100) = 10
Similarly, the number of blocks for the Project relation can be calculated as:
Number of blocks for Project relation = ceil(2000 / 100) = 20
Now, let's calculate the number of common blocks. Since the number of distinct EmployeeIDs is 1000 and the number of blocks for the Employee relation is 10, each block in the Employee relation will have 100 distinct EmployeeIDs. Therefore, the number of common blocks can be calculated as:
Number of common blocks = (Number of distinct EmployeeIDs / EmployeeIDs_per_block) = (1000 / 100) = 10
Using the formula mentioned earlier, we can calculate the number of block transfers in the worst case as:
Number of block transfers = (Number of blocks in the Employee relation) + (Number of blocks in the Project relation) - (Number of common blocks)
= 10 + 20 - 10
= 20
Therefore, the number of block transfers in the worst case for the Natural Join of the two relations is 20, which corresponds to option A.