Given the following table: library(book_id,book_title,person_id,due_date,first_n

Question

Given the following table:

library(book_id,book_title,person_id,due_date,first_name,last_name,returned_date,late_fee)

With the following assumptions: -

One copy of each book is held by the library -

Person_id is unique for each person, book_id is unique for each book -

The library table is meant to store information about loans of books made by the library.

Here are the functional dependencies for the above table:

Book_id book_title

Person_id first_name,last_name

Book_id,person_id,due_date returned_date,late_fee

Give an example of update anomaly for this table

ANY HELP PLEASE...ANY EXPLANATION WOULD BE REALLY HELPFUL :)

Explanation / Answer

Suppose we have the following entries in the library table-

The above relation follows all the assumptions and functional dependencies. Also there can be a possibility that the same person can loan many books because it is not mentioned that one person can loan only one book.

Now suppose if there is an error in the person's name or id then it must be updated in multiple entries in the table .

For example, if there is an error in the name of person with P1 id then his name must be updated 3 times as he has entries thrice since he has issued 3 books. So if the update is not performed correctly at all places then it will lead to inconsistent data.

Thus this is only update anomaly where we have inconsistent data due to improper or incorrect update operation of redundant data.

Please ask if any query regarding the answer.

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