Insertion and deletion anomalies

Question

Illustrate briefly the term insertion and deletion anomalies?

Answer 1

A deletion anomaly takes places when, by deleting the facts regarding one entity, we inadvertently delete facts regarding another entity; with one deletion, we lose facts regarding two entities. For illustration, if we delete the tuple for Student 001289 from a table, we might lose not only the fact that Student 001289 is in Pierce Hall, but as well the fact that he has $200 left in his security deposit.

An insertion anomaly takes places when we encounter the restriction which we cannot insert a fact regarding one entity till we have an additional fact regarding another entity. For illustration, we want to store the fact which the security deposit for Pierce Hall is $300, but we can’t enter this data into the Student relation till a student registers for Pierce Hall.