Solution

The correct answer is In a row of relational table, an attribute can have more than one value

Key Points

• In a relational database model, each attribute of a tuple (or row) must have only one value.
• This is a reflection of the atomicity property of the relational model.
• If more than one value is required, it should be represented as another row, or possibly in another table depending on the relationship.
• This is to maintain the integrity and simplicity of the design.
• However, it's worth mentioning that some modern DBMS do support multi-valued attributes, although this is outside the scope of the classical relational model.

Additional Information

•  An attribute in an ER diagram refers to a property or characteristic of an entity or relationship. In a relational model, it's equivalent is a table column.
• In ER modeling, an attribute can be single-valued or multi-valued. However, in a strict relational database model, each attribute of a row must have a single value (atomicity). If multiple values are needed, they can be normalized and placed in separate rows or tables.
• A composite attribute can be divided into smaller sub-attributes, which come together to represent a fuller concept. For example, an entity "Person" might have a composite attribute "Full Name", subdivided into "First Name" and "Last Name".
• In relational model, an attribute in a row can hold a single value or be marked as NULL, representing the absence of a value or unknown information.