Course: Database Systems Discussion 1 (Chapter 14): Discuss insertion, deletion, and modification anomalies. Why are they considered bad? Illustrate with examples. Instructions: Your response to th
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Post 1:
Ricardo
Ricardo dis 1
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Hello Class,
For this week’s first discussion, we are asked to examine the notion of insert, update, and delete anomalies. For databases to maintain integrity, these types of anomalies should be cause for concern. Database administrators should be aware of risk factors related to these types of anomalies and ensure best practices are observed in the design, architecture, and maintenance of the system. According to Ale & Espil, database integrity can be a major factor in the failure of a database system (Ale & Espil, 2002).
The first negative consequence of these types of anomalies is consistency. When these errors occur, the resources needed to maintain data consistency is large. Additionally, these types of anomalies can lead to redundant data. Data redundancy can affect the performance and reliability of the database system. Furthermore, redundancy can lead to memory usage that will be wasted at the OS level. An additional negative effect is the unnecessary updates that may occur, leading to more wasted resources.
Insertion anomalies occur during the insertion of a new record in the database. If there is no constraint on a particular field, invalid data can cause discrepancies across the database. Next, deletion anomalies can lead to corrupt data due to invalid deletions or deletions due to a cascade effect. For example, if there was a table of locations, and the only row in the table was deleted, it could lead to anomalies. Finally, the Encyclopedia of Database Systems states that the major problem resulting from data redundancy in an un-normalized database table are collectively known as update anomalies (“Database Anomalies,” 2009). These concepts become even more critical as RDBMS solutions require a high level of integrity to provide reliability, performance, and availability.
Regards,
Ricardo Scarello
References
Ale, J. M., & Espil, M. M. (2002). Integrity constraints in an active database environment. Database Integrity, 113-143. https://doi.org/10.4018/978-1-930708-38-9.ch004
Data anomalies. (2009). Encyclopedia of Database Systems, 557-557. https://doi.org/10.1007/978-0-387-39940-9_2341
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Post 2
2 days ago
Brittany
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Anomalies
Insertion Anomalies insert data into a database whether it is for tuples or values under an entity. This anomaly can be considered "bad" as not all attributes will have values that correspond with them, causing a NULL insertion to occur. Another reason why this anomaly may be looked upon as "bad" is because if the values that are being inserted are not inserted correctly or in a consistent manner, it then ruins the flow of the way the information can be stored (Elmarsi & Navathe, 2017). For example, if you have an entity named "Student" and the following attributes "First Name" Student ID" and "Last Name", it is possible to insert the following information. If you have another entity named "Class" that has a relationship with "Student", it may be hard to insert values for "CourseID", "ClassName", "Professor", and "ClassDate" as some Students may not be taking certain classes depending on the grade level and the semester the course is offered.
Deletion Anomalies correspond with insertion anomalies as some information may end up being too redundant which results in data being lost as the tuples are being stored separately (Elmarsi & Navathe, 2017). If using the Modification Anomaly, all data must be changed if one value of the attribute is changed as this confuses the data making the values inconsistent. The last two anomalies tie into the first anomaly making all three be considered "bad" as they cause problems and unecessary updates to be made. There are guidelines to help avoid these errors such as designing a base relation schema so that no insertion, deletion, or modification anomaly are present in the relations at all (Elmarsi & Navathe, 2017).
References
Elmarsi, Ramez & Navathe, Shamkant. (2017). "Fundamentals of Database Systems". Pearson Educated Limited.
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