Question

Multi-valued fields in relational databases are:

1) Allowed in line item tables
2) Allowed because they make update queries faster
3) Allowed because they make the retrieving of data in a query faster
4) Not allowed
5) 2 of the above are correct

Answer 1

Relational databases do not allow multi-valued fields as they violate the principle of the First Normal Form. Instead, a separate line item table should be used for storing multiple values for a single attribute, maintaining data integrity and simplifying queries. The correct multiple-choice option is (4) Not allowed.

Step-by-step explanation:

In relational database design, a fundamental rule is to avoid multi-valued fields because they violate one of the core principles of database normalization, specifically the First Normal Form (1NF). According to 1NF, each column in a table should hold atomic values, meaning that the values are indivisible. This ensures data integrity, reduces redundancy, and simplifies the SQL queries used for data manipulation. Therefore, the correct answer is (4) Not allowed because multi-valued fields can lead to anomalies and complicate queries, making updates, deletions, and data retrieval more complex.

However, in specific use cases, multi-valued fields might appear to be a practical solution, for example, in a NoSQL or non-relational database where one-to-many relationships are handled differently. But in a classic relational database context, if one needs to store multiple values for a single attribute, creating a separate line item table, known as a junction or link table, is the appropriate approach. This maintains normalization and avoids multi-valued fields in a single table. The correct multiple-choice option is (4) Not allowed.