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 | Sams Teach Yourself SQL in 24 Hours, Third Edition
By Ronald R. Plew, Ryan K. Stephens
| | Table of Contents | | | | Appendix C. Answers to Quizzes and Exercises |
Hour 2, "Defining Data Structures" Quiz Answers | 1: | True or false: An individual's Social Security number can be any of the following data types: constant-length character, varying-length character, numeric. | | A1: | True, as long as the precision is the correct length. | | 2: | True or false: The scale of a numeric value is the total length allowed for values. | | A2: | False. The precision is the total length, where the scale represents the number of places reserved to the right of a decimal point. | | 3: | Do all implementations use the same data types? | | A3: | No. Most implementations differ in their use of data types. The data types prescribed by ANSI are adhered to, but may differ between implementations according to storage precautions taken by each vendor. | | 4: | What are the precision and scale of the following? DECIMAL(4,2) DECIMAL(10,2) DECIMAL(14,1) | | A4: | -
DECIMAL(4,2) -
precision = 4, scale = 2 -
DECIMAL(10,2) -
precision = 10, scale = 2 -
DECIMAL(14,1) -
precision = 14, scale = 1 | | 5: | Which numbers could be inserted into a column whose data type is DECIMAL(4,1)? -
16.2 -
116.2 -
16.21 -
1116.2 -
1116.21 | | A5: | The first three fit, although 16.21 is rounded off. The numbers 1116.2 and 1116.21 exceed the maximum precision, which was set at 4. | | 6: | What is data? | | A6: | Data is a collection of information stored in a database as one of several different data types. | Exercise Answers | 1: | Take the following column titles, assign them to a data type, and decide on the proper length. -
ssn -
state -
city -
phone_number -
zip -
last_name -
first_name -
middle_name -
salary -
hourly_pay_rate -
date_hired | | A1: | -
SSN constant-length character -
CITY varying-length character -
STATE varying-length character -
ZIP constant-length character -
PHONE_NUMBER constant-length character -
LAST_NAME varying-length character -
FIRST_NAME varying-length character -
MIDDLE_NAME varying-length character -
SALARY numeric data type -
HOURLY_PAY_RATE decimal -
DATE_HIRED date | | 2: | Take the same column titles and decide whether they should be NULL or NOT NULL, realizing that in some cases where a column would normally be NOT NULL, the column could be NULL or vice versa, depending on the application. -
ssn -
state -
city -
phone_number -
zip -
last_name -
first_name -
middle_name -
salary -
hourly_pay_rate -
date_hired | | A2: | -
SSN NOT NULL -
STATE NOT NULL -
CITY NOT NULL -
PHONE_NUMBER NULL -
ZIP NOT NULL -
LAST_NAME NOT NULL -
FIRST_NAME NOT NULL -
MIDDLE_NAME NULL -
SALARY NULL -
HOURLY_PAY_RATE NULL -
DATE_HIRED NOT NULL Every individual may not have a phone (however rare that may be) and not everyone has a middle name , so these columns should allow NULL values. In addition, not all employees are paid an hourly rate. | | 3: | We are going to set up a database in MySQL to use for the subsequent hours in this book. From Windows Explorer, go to the folder where you installed MySQL on your computer. Double-click on the bin folder, and then double click on the executable file called mysql.exe. If you receive an error stating that the server could not be found, first execute winmysqladmin.exe from the bin folder, and then enter a username and password. After the server is started, execute mysql.exe from the bin folder. At the mysql> command prompt, enter the following command to create a database to use for this book's exercises: create database learnsql; Be sure to press the Enter key on your keyboard after entering the command. For all subsequent hands-on exercises in this book, you will double-click on the mysql.exe executable, and then enter the following command to use the database you just created: use learnsql; | |
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