Implementing relationships:\n“A foreign key is used to implement relationships between tables.”\nEvaluate the statement’s correctness in standard relational modeling.

Introduction / Context:
Relations (tables) in a database model real-world associations: Orders belong to Customers, LineItems belong to Orders, and so on. The mechanism that enforces these associations is the foreign key constraint. This item checks your understanding of how relational links are realized technically.

Given Data / Assumptions:

• A “foreign key” is one or more columns in a child table referencing a candidate key (usually the primary key) of a parent table.
• DBMS enforces referential integrity, preventing orphaned child rows and ensuring key consistency.
• Both natural and surrogate parent keys may be referenced.

Concept / Approach:
A foreign key defines and enforces the relationship between two tables. It constrains allowed values in the child table’s referencing column(s) to those that exist in the parent table’s referenced key. This enforces “existence dependency” and allows the DBMS to support ON DELETE/ON UPDATE actions like RESTRICT, CASCADE, SET NULL, or SET DEFAULT. The choice between natural and surrogate keys is orthogonal: the foreign key mechanism works for either.

Step-by-Step Solution:

Verification / Alternative check:
Attempting to insert a child referencing a non-existent parent key will fail; deleting a parent with existing children will follow configured action (RESTRICT, CASCADE, etc.).

Why Other Options Are Wrong:

• “Incorrect” contradicts standard practice.
• “Only true for natural/composite keys” is false; foreign keys operate regardless of key type or cardinality.
• Isolation level governs concurrency, not referential structure.

Common Pitfalls:
Not indexing foreign key columns; mismatched data types or collations between parent and child; trying to enforce relationships purely in application code.

Final Answer:
Correct