Learning PHP, MySQL, and JavaScript

Chapter 9 Answers

Question 9-1

The term relationship refers to the connection between two pieces of data that have some association, such as a book and its author, or a book and the customer who bought the book. A relational database such as MySQL specializes in storing and retrieving such relations.

Question 9-2

The process of removing duplicate data and optimizing tables is called normalization.

Question 9-3

The three rules of First Normal Form are: (1) There should be no repeating columns containing the same kind of data; (2) All columns should contain a single value; and (3) There should be a primary key to uniquely identify each row.

Question 9-4

To satisfy Second Normal Form, columns whose data repeats across multiple rows should be removed to their own tables.

Question 9-5

In a one-to-many relationship, the primary key from the table on the “one” side must be added as a separate column (a foreign key) to the table on the “many” side.

Question 9-6

To create a database with a many-to-many relationship, you create an intermediary table containing keys from two other tables. The other tables can then reference each other via the third.

Question 9-7

To initiate a MySQL transaction, use either the BEGIN or the START TRANSACTION command. To terminate a transaction and cancel all actions, issue a ROLLBACK command. To terminate a transaction and commit all actions, issue a COMMIT command.

Question 9-8

To examine how a query will work in detail, you can use the EXPLAIN command.

Question 9-9

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