ER-to-Relational Mapping — Ternary Relationship with an Associative Entity When mapping a ternary relationship that has been modeled with an associative (intersection) entity, which statement correctly describes the number of relations (tables) created?

Introduction:
Ternary relationships connect three entity types simultaneously. In many methodologies, especially when there are attributes on the relationship or business rules to capture, we model a ternary relationship as an associative entity. Understanding how this maps into the relational model ensures correct representation of the three-way association and its attributes.

Given Data / Assumptions:

• There are three regular entity types participating, each mapped to its own relation.
• The ternary relationship is represented as an associative entity with its own attributes (possibly including a surrogate key).
• Standard ER-to-relational rules are applied.

Concept / Approach:
Each of the three regular entities becomes one relation. The associative entity, which captures the ternary relationship and any attributes on that relationship, becomes a fourth relation. The associative relation typically includes foreign keys referencing the three participating entity relations, and may define a composite primary key or a surrogate primary key with unique constraints over the three foreign keys.

Step-by-Step Solution:
Map Entity A to Relation A, Entity B to Relation B, and Entity C to Relation C.Create Relation R for the associative entity representing the ternary relationship.Include foreign keys in R: A_id, B_id, C_id referencing A, B, C respectively.Define the primary key as either (A_id, B_id, C_id) or a surrogate key with a unique constraint on those three columns.

Verification / Alternative check:
Compare to the mapping for binary relationships with an associative entity: the count increases by one for each additional base entity and one for the associative entity itself. For ternary, that totals four relations (three entities plus one associative relation).

Why Other Options Are Wrong:

• One or two relations ignore the necessary representation of all participants.
• Three relations omit the associative entity relation.
• Conditional creation based on mandatory participation does not remove the need for the associative relation.

Common Pitfalls:
Trying to decompose a ternary directly into three separate binaries without preserving the intended three-way constraint, which can change semantics.

Final Answer:
Four relations are created.