Optionality and insertion order:\n“When the parent entity is required, a new parent row can always be inserted.”\nAssess whether this statement aligns with relational integrity and typical DBMS behavior.

Introduction / Context:
In modeling, “parent required” usually means a child cannot exist without a valid parent (the relationship is mandatory on the child side). This item checks whether such a rule affects the ability to create a new parent row by itself.

Given Data / Assumptions:

• Parent–child relationship enforced by a foreign key in the child referencing the parent’s key.
• “Parent required” refers to the child’s mandatory dependency, not a requirement that a parent must have at least one child at creation time.
• Standard DBMS enforcement: foreign key checks on child inserts/updates; parents can exist independently unless additional constraints are modeled.

Concept / Approach:
Foreign key constraints prevent children from referencing non-existent parents, but they do not prevent creating parent rows without children. In most DBMSs, minimum cardinality rules on the parent side (for example, “every parent must have at least one child”) are not enforced natively. Enforcing such a rule would typically require triggers, assertions, or application logic. Therefore, even when the relationship is mandatory from the child’s perspective, you can always insert a parent row—there is no referential integrity violation because no child exists yet.

Step-by-Step Solution:

Verification / Alternative check:
Test in a relational engine: parent inserts succeed with or without children; child inserts require an existing parent.

Why Other Options Are Wrong:

• “Only after a child row exists” inverts the dependency and is not enforced by foreign keys.
• Deferrable constraints affect timing of checks, not the basic ability to insert a stand-alone parent.
• Index structure has no bearing on this rule.

Common Pitfalls:
Misreading “parent required” as “parent must have at least one child immediately”; assuming DBMS natively enforces minimum cardinality on the parent side.

Final Answer:
Correct