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Microsoft Exam 77-885 Topic 5 Question 1 Discussion
Topic #: 5
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?
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.
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