The table shown in Figure 1 is susceptible to update anomalies. Provide examples
ID: 3700796 • Letter: T
Question
The table shown in Figure 1 is susceptible to update anomalies. Provide examples of insertion, deletion, and modification anomalies.
staffNo dentistName patientNo patientName surgeryNo appointment date 12-Aug-03 10.00 13-Aug-03 12.00 S15 12-Sept-03 10.00 14-Sept-03 10.00 14-Oct-03 16.30 15-Oct-03 18.00 time S1011 S1011 S1024 S1024 S1032 S1032 S10 Tony Smit?h Tony Smit?h Helen Pearson P108 Helen Pearson P108 Robin Plevin Robin Plevin Gillian White ill Bell Ian MacKay Ian MacKay Jill Bell John Walker P100 P105 S10 S10 S15 S13 P105 P110 Figure 1: Details of patient dental appointments.Explanation / Answer
Insertion anomalies:
It occurs when certain attributes cannot be inserted into the table without the presence of other attributes. In this given example we cannot insert any dentist information who have not done any surgery yet. This is an example of insert anomalies.
Deletion anomalies:
It occurs when certain attributes are lost because of the deletion of other attributes. In this example if we want to delete a dentist information from the table say we want to delete Tony Smith then some patient details like Gillian White will also be lost. This is an example of Deletion anomalies.
Modification anomalies:
It occurs when certain attributes need to be changed and if the change need to be done more than one places in a table and if some are missed by chance then anomalies happens in database. These anomalies often occur by the addition of, change to, or deletion of data from a database table. In this example if we need to change Dentist name say Tony Smith to Tony Denver then we have to check minutely where this attribute occurs and we have to change all the places accordingly, if we miss one of them then modification anomalies occurs. In another way if Insert anomaly or deletion anomaly occurs then also Modification anomalies occur.
Hope this helps. Thanks.
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