A descriptive attribute is a type of attribute in a database that describes a characteristic or property of an entity, but does not contribute to the identity or uniqueness of the entity. In other words, a descriptive attribute is not a key attribute, and it does not have the ability to uniquely identify an entity.
For example, consider a database for an e-commerce website that includes an entity called 'Product'. The 'Product' entity might have key attributes like 'Product ID' and 'Product Name' that uniquely identify each product, but it might also have descriptive attributes like 'Description', 'Price', 'Manufacturer', and 'Weight'. These attributes provide additional information about the product, but do not contribute to the uniqueness of the product.
Descriptive attributes can be used to provide additional information about an entity, and can be useful for queries or reporting. For example, if a customer is searching for a product on the e-commerce website, they might want to know the price, manufacturer, or weight of the product. The descriptive attributes can be used to provide this information, even though they do not uniquely identify the product.
In an ER diagram, descriptive attributes are typically represented as regular attributes without any underline or special notation, to differentiate them from key attributes.
