GATE CS 2012 Q14 — ER-model

To determine which statement is INCORRECT, let us analyze the properties of both the Entity-Relationship (ER) model and the Relational model:

• Option A: In the basic ER model, attributes can be multivalued (for example, a Phone_Number attribute can store multiple phone numbers for a single entity). Thus, this statement is correct.
• Option B: In the ER model, attributes can be composite (for example, a Name attribute can be composed of First_Name and Last_Name). Thus, this statement is correct.
• Option C: In the relational model, relations are strictly based on the first normal form (1NF) by definition. This requires all attribute values in any row to be atomic (indivisible). Consequently, an attribute in a row of a relational table cannot contain multiple values. Thus, this statement is incorrect.
• Option D: In a relational table, each attribute value in a row must be either a single atomic value or a NULL value (representing a missing or inapplicable value). Thus, this statement is correct.

Since the question asks for the INCORRECT statement, the correct option is C.