ITPEC FE Morning October 2019 Question 28

Foreign Key Purpose — referential integrity constraint between related tables.

A foreign key ensures that a value in the child table must exist in the parent table's primary key column.

• •Referential integrity — prevents orphan records (e.g., an order referencing a non-existent customer)
• •Blocks INSERT of invalid references and DELETE of referenced parent rows

Why not others:
- (a) Prevent fragmentation — physical storage issue, solved by reorganization, not foreign keys
- (c) Restore records after failure — handled by backup/recovery and transaction logs
- (d) Speed up searching — handled by indexes and clustering, not foreign keys

Key rule: Foreign key = constraint for consistency, not performance or recovery.

AI-generated — may contain errors