Database Physical Design - Quiz Explanation

The answers you selected are indicated below, along with text that explains the correct answers.

1.	If database users often call on a few columns in a table when they create joins and views, you might be able to improve database performance using what technique? Please select the best answer.
	A.	Clustering
	B.	Indexing
	C.	Horizontal partitioning
	D.	Vertical partitioning
	The correct answer is D. You could improve database performance in this situation using vertical partitioning. A is incorrect because clustering moves frequently joined records from more than one table to a specific area of the hard drive. B is incorrect because indexing a field does not prevent the RDBMS from searching the entire table. C is incorrect because horizontal partitioning divides the records in a table into two or more smaller tables, which does not help a user if they only need the values in a few table columns.

2.	What kind of table fields will an RDBMS index automatically? Please select the best answer.
	A.	Foreign key fields
	B.	Primary key fields
	C.	No fields
	D.	All fields
	The correct answer is B. An RDBMS automatically indexes values in primary key fields. A is incorrect because, while indexing a foreign key field will often improve database performance (especially for joins), it is not done automatically. C is incorrect because every RDBMS will create an index of primary key field values. D is incorrect because creating unnecessary indexes often hurts database performance.

3.	Dividing records from a single table into two or more smaller tables is an example of what process? Please select the best answer.
	A.	Horizontal partitioning
	B.	Vertical partitioning
	C.	Indexing
	D.	Clustering
	The correct answer is A. Dividing records from a single table into two or more smaller tables is an example of horizontal partitioning. B is incorrect because vertical partitioning divides a table into two or more smaller tables consisting of every record in the table, but with the columns dividing between the tables. C is incorrect because indexing causes the RDBMS to create and maintain an internal record of the values in a field. D is incorrect because clustering moves frequently joined records from more than one table to a specific area of the hard drive, but does not divide a single table into two or more smaller tables.

4.	Which definition best reflects the role of the data dictionary? Please select the best answer.
	A.	An index of values in a primary key field
	B.	An index of values in all primary key fields
	C.	A set of tables listing all changes to a database
	D.	A set of tables defining the structure of a database
	The correct answer is D. The data dictionary is a set of tables defining the structure of a database. A and B are incorrect because indexes of primary key fields are stored outside the data dictionary. C is incorrect because the data dictionary contains the entire structure of the database, not just changes from the original structure.