You work as a Database Designer for Tech Perfect Inc. The company has a Windows Vista-based
computer with Microsoft Office 2010 installed on it. The computer contains two databases named
Shippers and Orders created in Microsoft Office Access 2010. A one-to-many relationship is created
between both tables. You want to delete a Shipper. The shipper that you want to delete has orders
in the Orders table. When you delete the Shipper record, these orders will become “orphans”. The
orders will still include a shipper ID, but this ID will not be valid. What will you do to prevent these orphans?
A.
Cascade delete related records.
B.
Enforce domain integrity.
C.
Cascade update related fields.
D.
Enforce referential integrity.
Explanation:
To prevent these orphans, you should enforce referential integrity. Referential integrity means that
the foreign key in any referencing table must always refer to a valid row in the referenced table.
Referential integrity ensures that the relationship between two tables remains synchronized during
updates and deletes. For a foreign key to be valid, it must contain either the value NULL, or an
existing key value from the primary or unique key columns referenced by the foreign key. To enforce
referential integrity, a foreign key column link to the primary key column should be created in the
related table.
Answer C is incorrect. You can cascade update related fields to update all affected rows as part of a
single operation.
Answer B is incorrect. Domain integrity enforces data validity by restricting the data type, valid
values (using CHECK constraints and rules), and range of possible values (using FOREIGN KEY
constraints) for columns in a table.
Answer A is incorrect. You can cascade delete related records to delete a row and all related
records.