Suppose the EMPLOYEE table is kept sorted by its primary key ssn. Draw a diagram

Question

Suppose the EMPLOYEE table is kept sorted by its primary key ssn. Draw a diagram of a possible secondary index on the attribute dno. Because dno is not a key, each index entry will contain a list of either record pointers or primarykey values from the EMPLOYEE table; be sure you show how these pointers / key-values are used.

Dno

1

4

5

Fname

Lname

Ssn

Dno

John

Smith

123456789

5

Franklin

Wong

333445555

1

Joyce

English

453453453

5

Ramesh

Narayan

666884444

4

James

Borg

888665555

1

Jennifer

Wallace

987654321

5

Dno

1

4

5

Explanation / Answer

It would be similar to below..

Dno => SSN

1 => 333445555 => 888665555
4 => 666884444
5 => 123456789 => 453453453 => 987654321

It is like a array corresponding to all different vaues(HashTable) storing the first node of that index.. The nodes itself contain the reference for the next node.. Very similar to HashTables using Linked List

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