Suppose we have a table and assumptions as follows: (every attribute is atomic)

Question

Suppose we have a table and assumptions as follows: (every attribute is atomic)

SEMINARS (Seminar#, Title, Room, Seminar_Date, Seminar_fee, Instructor#, Instructor_Name, Honorarium, Student#, Student_name, Regsitration_date, Registration fee)

- A seminar has a fixed title and fee.

- Each seminar is always held in the same room, regardless of days offered

- A seminar is one-day long, but held many times over the period.

- Each seminar is always taught by the same instructor.

- One instructor may teach multiple seminars and receive a different honorarium for different seminars.

- A student can register a particular seminar that is held in a particular date.

- If you register 30 days early for a particular seminar, you pay an early-bird fee which is 20% cheaper than a regular registration fee.

- A student can register multiple seminars at different dates.

Give an example of the following anomaly from SEMINARS table. Use English

Insert

Update

Delete

Explanation / Answer

Examples of anomalies from SEMINARS table

Insert --- If a new Student join the institution , his details need to be inserted in the table . But along with that Seminar details needs to be inserted . If the student is not assigned any Seminar, the Seminar# should be inserted NULL which is not allowed as Seminar# is the primary key of the table . Hence Student information should be separately stored in another table.

Update --- If we want to change the Seminar_date , we must update all the instructors and student records who are participating in that Seminar. If this updation is not done on all the relevant rows, inconsistency occurs in the database.

Delete --- If we delete a row containing the information of last instructor in the Seminar, the whole information about the Seminar will also be deleted. We will lost information about that Seminar also.

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