How are multivalued attributes handled in database design?

Multivalued attributes in database design are typically handled by creating separate tables or using a complex data type.

In the context of database design, multivalued attributes are those that can have more than one value for a particular entity. For instance, a person can have multiple phone numbers or email addresses. These attributes pose a challenge in database design as they violate the rules of the first normal form (1NF), which states that each attribute of a table must have an atomic (indivisible) value.

One common way to handle multivalued attributes is by creating separate tables. For example, if we have a 'Person' table with a multivalued attribute 'Phone Numbers', we can create a separate 'Phone Numbers' table. This table would have two columns: 'Person ID' and 'Phone Number'. Each row in this table would represent a single phone number for a person. The 'Person ID' would be a foreign key linking back to the 'Person' table. This way, we can store multiple phone numbers for each person, and the data remains in first normal form. For a deeper understanding of database systems, you may explore topics on DBMS and RDBMS.

Another approach is to use a complex data type, such as an array or a JSON object, to store the multiple values of an attribute. This approach is supported by some modern database management systems (DBMSs) like PostgreSQL. However, this method can make querying and manipulating the data more complex and may not be as efficient as the separate table approach. Understanding the data and databases foundational concepts can help clarify these approaches.

In some cases, multivalued attributes can be handled by concatenating the values into a single string, with a delimiter to separate each value. This approach is generally not recommended, as it can make querying and manipulating the data difficult and can lead to data anomalies. Further insight into how different database models handle such attributes could be beneficial.

A-Level Computer Science Tutor Summary: In database design, when an attribute has more than one value, like a person having multiple phone numbers, we handle it by creating a new table or using complex types like arrays. The new table links back to the original using a foreign key. Although we can also join values into a string or use complex data types, these methods can complicate things.