What anomaly occurs when wanted data is deleted from a relation?

A deletion anomaly occurs when the deletion of data from a relational database unintentionally removes not only the targeted data but also other valuable information that is related to it. This problem typically arises in poorly designed databases where multiple types of data are stored in a single table.

For instance, if a database table contains both customer information and their associated orders, deleting a customer record may also lead to the loss of crucial order details that are pertinent to that customer. Therefore, while the intention may be to remove a single entry, related data is also lost, which can compromise the integrity and completeness of the database.

This is why choosing deletion anomaly as the answer highlights a significant concern in database design: ensuring that information is organized in a way that protects it from unintentional loss during deletion operations. In contrast, the other types of anomalies, such as insertion and update anomalies, refer to different issues related to the manipulation of data, but they do not specifically address the consequences of deleting information.