Regarding Indexes, which of the following options is correct?

The correct answer is that unique indexes help prevent data duplication. In database management, a unique index ensures that all values in a specified column or a set of columns are distinct. This characteristic is essential for maintaining data integrity, especially when dealing with identifiers, such as user IDs or email addresses, where duplicates could lead to ambiguity and inconsistencies.

By using unique indexes, the database enforces a rule that does not allow the insertion of duplicate values into the indexed columns. Consequently, if an attempt is made to insert a duplicate value, the database will trigger an error, thus enforcing the uniqueness constraint. This capability is crucial in applications that require consistent and reliable data, such as registration systems or inventory databases.

Other options mention elements related to indexes, but they do not accurately represent how indexes function. For example, the claim that custom indexes cannot be added to an Entity is not true, as developers can indeed create custom indexes to optimize specific queries. Also, while indexes do speed up data retrieval, they can introduce some overhead during data modification processes, such as inserts, updates, or deletes, due to the need to maintain the index structure. Lastly, the idea that indexes over referenced attributes cannot be deleted is misleading, as it's typically possible to delete an index