Given the basic E R diagram and relational model, which of the the following is incorrect?

Question

Question

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UGC NET Computer Science (Paper 2) 17 June 2023 Official Paper

An attribute of an entity can have more than one value
An attribute of an entity can be composite
In a row of relational table, an attribute can have more than one value
In a row of a relational table, an attribute can have exactly one value or a NULL value

Answer 1

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.