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📄 Contents

  1. Sams Teach Yourself SQL in 24 Hours, Third Edition
  2. Table of Contents
  3. Copyright
  4. About the Authors
  5. Acknowledgments
  6. Tell Us What You Think!
  7. Introduction
  8. Part I: A SQL Concepts Overview
  9. Hour 1. Welcome to the World of SQL
  10. SQL Definition and History
  11. SQL Sessions
  12. Types of SQL Commands
  13. An Introduction to the Database Used in This Book
  14. Summary
  15. Q&A
  16. Workshop
  17. Part II: Building Your Database
  18. Hour 2. Defining Data Structures
  19. What Is Data?
  20. Basic Data Types
  21. Summary
  22. Q&A
  23. Workshop
  24. Hour 3. Managing Database Objects
  25. What Are Database Objects?
  26. What Is a Schema?
  27. A Table: The Primary Storage for Data
  28. Integrity Constraints
  29. Summary
  30. Q&A
  31. Workshop
  32. Hour 4. The Normalization Process
  33. Normalizing a Database
  34. Summary
  35. Q&A
  36. Workshop
  37. Hour 5. Manipulating Data
  38. Overview of Data Manipulation
  39. Populating Tables with New Data
  40. Updating Existing Data
  41. Deleting Data from Tables
  42. Summary
  43. Q&A
  44. Workshop
  45. Hour 6. Managing Database Transactions
  46. What Is a Transaction?
  47. What Is Transactional Control?
  48. Transactional Control and Database Performance
  49. Summary
  50. Q&A
  51. Workshop
  52. Part III: Getting Effective Results from Queries
  53. Hour 7. Introduction to the Database Query
  54. What Is a Query?
  55. Introduction to the <tt>SELECT</tt> Statement
  56. Examples of Simple Queries
  57. Summary
  58. Q&amp;A
  59. Workshop
  60. Hour 8. Using Operators to Categorize Data
  61. What Is an Operator in SQL?
  62. Comparison Operators
  63. Logical Operators
  64. Conjunctive Operators
  65. Negating Conditions with the <tt>NOT</tt> Operator
  66. Arithmetic Operators
  67. Summary
  68. Q&amp;A
  69. Workshop
  70. Hour 9. Summarizing Data Results from a Query
  71. What Are Aggregate Functions?
  72. Summary
  73. Q&amp;A
  74. Workshop
  75. Hour 10. Sorting and Grouping Data
  76. Why Group Data?
  77. The <tt>GROUP BY</tt> Clause
  78. <tt>GROUP BY</tt> Versus <tt>ORDER BY</tt>
  79. The <tt>HAVING</tt> Clause
  80. Summary
  81. Q&amp;A
  82. Workshop
  83. Hour 11. Restructuring the Appearance of Data
  84. The Concepts of ANSI Character Functions
  85. Various Common Character Functions
  86. Miscellaneous Character Functions
  87. Mathematical Functions
  88. Conversion Functions
  89. The Concept of Combining Character Functions
  90. Summary
  91. Q&amp;A
  92. Workshop
  93. Hour 12. Understanding Dates and Times
  94. How Is a Date Stored?
  95. Date Functions
  96. Date Conversions
  97. Summary
  98. Q&amp;A
  99. Workshop
  100. Part IV: Building Sophisticated Database Queries
  101. Hour 13. Joining Tables in Queries
  102. Selecting Data from Multiple Tables
  103. Types of Joins
  104. Join Considerations
  105. Summary
  106. Q&amp;A
  107. Workshop
  108. Hour 14. Using Subqueries to Define Unknown Data
  109. What Is a Subquery?
  110. Embedding a Subquery Within a Subquery
  111. Summary
  112. Q&A
  113. Workshop
  114. Hour 15. Combining Multiple Queries into One
  115. Single Queries Versus Compound Queries
  116. Why Would I Ever Want to Use a Compound Query?
  117. Compound Query Operators
  118. Using an <tt>ORDER BY</tt> with a Compound Query
  119. Using <tt>GROUP BY</tt> with a Compound Query
  120. Retrieving Accurate Data
  121. Summary
  122. Workshop
  123. Q&amp;A
  124. Part V: SQL Performance Tuning
  125. Hour 16. Using Indexes to Improve Performance
  126. What Is an Index?
  127. How Do Indexes Work?
  128. The <tt>CREATE INDEX</tt> Command
  129. Types of Indexes
  130. When Should Indexes Be Considered?
  131. When Should Indexes Be Avoided?
  132. Summary
  133. Q&amp;A
  134. Workshop
  135. Hour 17. Improving Database Performance
  136. What Is SQL Statement Tuning?
  137. Database Tuning Versus SQL Tuning
  138. Formatting Your SQL Statement
  139. Full Table Scans
  140. Other Performance Considerations
  141. Performance Tools
  142. Summary
  143. Q&amp;A
  144. Workshop
  145. Part VI: Using SQL to Manage Users and Security
  146. Hour 18. Managing Database Users
  147. Users Are the Reason
  148. The Management Process
  149. Tools Utilized by Database Users
  150. Summary
  151. Q&amp;A
  152. Workshop
  153. Hour 19. Managing Database Security
  154. What Is Database Security?
  155. How Does Security Differ from User Management?
  156. What Are Privileges?
  157. Controlling User Access
  158. Controlling Privileges Through Roles
  159. Summary
  160. Q&amp;A
  161. Workshop
  162. Part VII: Summarized Data Structures
  163. Hour 20. Creating and Using Views and Synonyms
  164. What Is a View?
  165. Creating Views
  166. Dropping a View
  167. What Is a Synonym?
  168. Summary
  169. Q&amp;A
  170. Workshop
  171. Hour 21. Working with the System Catalog
  172. What Is the System Catalog?
  173. How Is the System Catalog Created?
  174. What Is Contained in the System Catalog?
  175. Examples of System Catalog Tables by Implementation
  176. Querying the System Catalog
  177. Updating System Catalog Objects
  178. Summary
  179. Q&amp;A
  180. Workshop
  181. Part VIII: Applying SQL Fundamentals in Today's World
  182. Hour 22. Advanced SQL Topics
  183. Advanced Topics
  184. Cursors
  185. Stored Procedures and Functions
  186. Triggers
  187. Dynamic SQL
  188. Call-Level Interface
  189. Using SQL to Generate SQL
  190. Direct Versus Embedded SQL
  191. Summary
  192. Q&amp;A
  193. Workshop
  194. Hour 23. Extending SQL to the Enterprise, the Internet, and the Intranet
  195. SQL and the Enterprise
  196. Accessing a Remote Database
  197. Accessing a Remote Database Through a Web Interface
  198. SQL and the Internet
  199. SQL and the Intranet
  200. Summary
  201. Q&amp;A
  202. Workshop
  203. Hour 24. Extensions to Standard SQL
  204. Various Implementations
  205. Examples of Extensions from Some Implementations
  206. Interactive SQL Statements
  207. Summary
  208. Q&amp;A
  209. Workshop
  210. Part IX: Appendixes
  211. Appendix A. Common SQL Commands
  212. SQL Statements
  213. SQL Clauses
  214. Appendix B. Using MySQL for Exercises
  215. Windows Installation Instructions
  216. Linux Installation Instructions
  217. Appendix C. Answers to Quizzes and Exercises
  218. Hour 1, "Welcome to the World of SQL"
  219. Hour 2, "Defining Data Structures"
  220. Hour 3, "Managing Database Objects"
  221. Hour 4, "The Normalization Process"
  222. Hour 5, "Manipulating Data"
  223. Hour 6, "Managing Database Transactions"
  224. Hour 7, "Introduction to the Database Query"
  225. Hour 8, "Using Operators to Categorize Data"
  226. Hour 9, "Summarizing Data Results from a Query"
  227. Hour 10, "Sorting and Grouping Data"
  228. Hour 11, "Restructuring the Appearance of Data"
  229. Hour 12, "Understanding Dates and Time"
  230. Hour 13, "Joining Tables in Queries"
  231. Hour 14, "Using Subqueries to Define Unknown Data"
  232. Hour 15, "Combining Multiple Queries into One"
  233. Hour 16, "Using Indexes to Improve Performance"
  234. Hour 17, "Improving Database Performance"
  235. Hour 18, "Managing Database Users"
  236. Hour 19, "Managing Database Security"
  237. Hour 20, "Creating and Using Views and Synonyms"
  238. Hour 21, "Working with the System Catalog"
  239. Hour 22, "Advanced SQL Topics"
  240. Hour 23, "Extending SQL to the Enterprise, the Internet, and the Intranet"
  241. Hour 24, "Extensions to Standard SQL"
  242. Appendix D. <tt>CREATE TABLE</tt> Statements for Book Examples
  243. <tt>EMPLOYEE_TBL</tt>
  244. <tt>EMPLOYEE_PAY_TBL</tt>
  245. <tt>CUSTOMER_TBL</tt>
  246. <tt>ORDERS_TBL</tt>
  247. <tt>PRODUCTS_TBL</tt>
  248. Appendix E. <tt>INSERT</tt> Statements for Data in Book Examples
  249. <tt>INSERT</tt> Statements
  250. Appendix F. Glossary
  251. Appendix G. Bonus Exercises
Recommended Book

Types of Joins

While different implementations have many ways of joining tables, you concentrate on the most common joins in this lesson. The types of joins that you learn are

EQUIJOINS 
NATURAL JOINS
NON-EQUIJOINS
OUTER JOINS
SELF JOINS

Component Locations of a Join Condition

As you have learned from previous hours, the SELECT and FROM clauses are both required SQL statement elements; the WHERE clause is a required element of a SQL statement when joining tables. The tables being joined are listed in the FROM clause. The join is performed in the WHERE clause. Several operators can be used to join tables, such as =, <, >, <>, <=, >=, !=, BETWEEN, LIKE, and NOT; they can all be used to join tables. However, the most common operator is the equal symbol.

Joins of Equality

Perhaps the most used and important of the joins is the EQUIJOIN, also referred to as an INNER JOIN. The EQUIJOIN joins two tables with a common column in which each is usually the primary key.

The syntax for an EQUIJOIN is

   syntax_icon.gif
SELECT TABLE1.COLUMN1, TABLE2.COLUMN2...
FROM TABLE1, TABLE2 [, TABLE3 ]
WHERE TABLE1.COLUMN_NAME = TABLE2.COLUMN_NAME
[ AND TABLE1.COLUMN_NAME = TABLE3.COLUMN_NAME ]

Look at the following example:

SELECT EMPLOYEE_TBL.EMP_ID,
       EMPLOYEE_PAY_TBL.DATE_HIRE
FROM EMPLOYEE_TBL,
       EMPLOYEE_PAY_TBL
WHERE EMPLOYEE_TBL.EMP_ID = EMPLOYEE_PAY_TBL.EMP_ID;

This SQL statement returns the employee identification and the employee's date of hire. The employee identification is selected from the EMPLOYEE_TBL (although it exists in both tables, you must specify one table), whereas the hire date is selected from the EMPLOYEE_PAY_TBL. Because the employee identification exists in both tables, both columns must be justified with the table name. By justifying the columns with the table names, you tell the database server where to get the data.

Data in the following example is selected from tables EMPLOYEE_TBL and EMPLOYEE_PAY_TBL tables because desired data resides in each of the two tables. An equality join is used.

   input_icon.gif

   SELECT EMPLOYEE_TBL.EMP_ID, EMPLOYEE_TB
   L.LAST_NAME,
       
   EMPLOYEE_PAY_TBL.POSITION

   FROM EMPLOYEE_TBL, EMPLOYEE_PAY_TBL

   WHERE EMPLOYEE_TBL.EMP_ID = EMPLOYEE_PAY_TBL.EMP_ID;

   output_icon.gif
EMP_ID    LAST_NAM POSITION
--------- -------- -------------
311549902 STEPHENS MARKETING
442346889 PLEW     TEAM LEADER
213764555 GLASS    SALES MANAGER
313782439 GLASS    SALESMAN
220984332 WALLACE  SHIPPER
443679012 SPURGEON SHIPPER

6 rows selected.

newterm_icon.gif

Notice that each column in the SELECT clause is preceded by the associated table name in order to identify each column. This is called qualifying columns in a query. Qualifying columns is only necessary for columns that exist in more than one table referenced by a query. You usually qualify all columns for consistency and to avoid any questions when debugging or modifying SQL code.

Natural Joins

A NATURAL JOIN is nearly the same as the EQUIJOIN; however, the NATURAL JOIN differs from the EQUIJOIN by eliminating duplicate columns in the joining columns. The JOIN condition is the same, but the columns selected differ.

The syntax is as follows:

   syntax_icon.gif
SELECT TABLE1.*, TABLE2.COLUMN_NAME
       [ TABLE3.COLUMN_NAME ]
FROM TABLE1, TABLE2 [ TABLE3 ]
WHERE TABLE1.COLUMN_NAME = TABLE2.COLUMN_NAME
[ AND TABLE1.COLUMN_NAME = TABLE3.COLUMN ]

Look at the following example:

SELECT EMPLOYEE_TBL.*, EMPLOYEE_PAY_TBL.SALARY 
FROM EMPLOYEE_TBL,
     EMPLOYEE_PAY_TBL
WHERE EMPLOYEE_TBL.EMP_ID = EMPLOYEE_PAY_TBL.EMP_ID;

This SQL statement returns all columns from EMPLOYEE_TBL and SALARY from the EMPLOYEE_PAY_TBL. The EMP_ID is in both tables, but is retrieved only from the EMPLOYEE_TBL because both contain the same information and do not need to be selected.

The following example selects all columns from the EMPLOYEE_TBL table and only one column from the EMPLOYEE_PAY_TBL table. Remember that the asterisk (*) represents all columns of a table.

   input_icon.gif

   SELECT EMPLOYEE_TBL.*, EMPLOYEE_PAY_TBL
   .POSITION

   FROM EMPLOYEE_TBL, EMPLOYEE_PAY_TBL

   WHERE EMPLOYEE_TBL.EMP_ID = EMPLOYEE_PAY_TBL.EMP_ID;

   output_icon.gif
EMP_ID    LAST_NAM FIRST_NA M ADDRESS       CITY         ST ZIP   PHONE
--------- -------- -------- - ------------- ------------ -- ----- ----------
PAGER      POSITION
---------- --------------
311549902 STEPHENS TINA     D RR 3 BOX 17A  GREENWOOD    IN 47890 3178784465
           MARKETING

442346889 PLEW     LINDA    C 3301 BEACON   INDIANAPOLIS IN 46224 3172978990
           TEAM LEADER

213764555 GLASS    BRANDON  S 1710 MAIN ST  WHITELAND    IN 47885 3178984321
3175709980 SALES MANAGER

313782439 GLASS    JACOB    3789 RIVER BLVD INDIANAPOLIS IN 45734 3175457676
8887345678 SALESMAN

220984332 WALLACE  MARIAH   7889 KEYSTONE   INDIANAPOLIS IN 46741 3173325986
           SHIPPER

443679012 SPURGEON TIFFANY  5 GEORGE COURT  INDIANAPOLIS IN 46234 3175679007
           SHIPPER


6 rows selected.

Using Table Aliases

newterm_icon.gif

The use of table aliases means to rename a table in a particular SQL statement. The renaming is a temporary change. The actual table name does not change in the database. As you will learn later in this hour, giving the tables aliases is a necessity for the SELF JOIN. Giving tables aliases is most often used to save keystrokes, which results in the SQL statement being shorter and easier to read. In addition, fewer keystrokes means fewer keystroke errors. Also, programming errors are typically less frequent if you can refer to an alias, which is often shorter in length and more descriptive of the data with which you are working. Giving tables aliases also means that the columns being selected must be qualified with the table alias. The following are some examples of table aliases and the corresponding columns:

SELECT E.EMP_ID, EP.SALARY, EP.DATE_HIRE, E.LAST_NAME 
FROM EMPLOYEE_TBL E,
     EMPLOYEE_PAY_TBL EP
WHERE E.EMP_ID = EP.EMP_ID
AND EP.SALARY > 20000;

analysis_icon.gif

The tables have been given aliases in the preceding SQL statement. The EMPLOYEE_TBL has been renamed E. The EMPLOYEE_PAY_TBL has been renamed EP. The choice of what to rename the tables is arbitrary. The letter E is chosen because the EMPLOYEE_TBL starts with E. Because the EMPLOYEE_PAY_TBL also begins with the letter E, you could not use E again. Instead, the first letter (E) and the first letter of the second word in the name (PAY) are used as the alias. The selected columns were justified with the corresponding table alias. Note that SALARY was used in the WHERE clause and must also be justified with the table alias.

Joins of Non-Equality

NON-EQUIJOIN joins two or more tables based on a specified column value not equaling a specified column value in another table. The syntax for the NON-EQUIJOIN is

   syntax_icon.gif
FROM TABLE1, TABLE2 [, TABLE3 ]
WHERE TABLE1.COLUMN_NAME != TABLE2.COLUMN_NAME
[ AND TABLE1.COLUMN_NAME != TABLE2.COLUMN_NAME ]

An example is as follows:

SELECT EMPLOYEE_TBL.EMP_ID, EMPLOYEE_PAY_TBL.DATE_HIRE 
FROM EMPLOYEE_TBL,
     EMPLOYEE_PAY_TBL
WHERE EMPLOYEE_TBL.EMP_ID != EMPLOYEE_PAY_TBL.EMP_ID;

analysis_icon.gif

The preceding SQL statement returns the employee identification and the date of hire for all employees who do not have a corresponding record in both tables. The following example is a join of non-equality:

   input_icon.gif

   SELECT E.EMP_ID, E.LAST_NAME, P.POSITIO
   N

   FROM EMPLOYEE_TBL E,
     
   EMPLOYEE_PAY_TBL P

   WHERE E.EMP_ID <> P.EMP_ID;

   output_icon.gif
EMP_ID    LAST_NAM POSITION
--------- -------- -------------
442346889 PLEW     MARKETING
213764555 GLASS    MARKETING
313782439 GLASS    MARKETING
220984332 WALLACE  MARKETING
443679012 SPURGEON MARKETING
311549902 STEPHENS TEAM LEADER
213764555 GLASS    TEAM LEADER
313782439 GLASS    TEAM LEADER
220984332 WALLACE  TEAM LEADER
443679012 SPURGEON TEAM LEADER
311549902 STEPHENS SALES MANAGER
442346889 PLEW     SALES MANAGER
313782439 GLASS    SALES MANAGER
220984332 WALLACE  SALES MANAGER
443679012 SPURGEON SALES MANAGER
311549902 STEPHENS SALESMAN
442346889 PLEW     SALESMAN
213764555 GLASS    SALESMAN
220984332 WALLACE  SALESMAN
443679012 SPURGEON SALESMAN
311549902 STEPHENS SHIPPER
442346889 PLEW     SHIPPER
213764555 GLASS    SHIPPER
313782439 GLASS    SHIPPER
443679012 SPURGEON SHIPPER
311549902 STEPHENS SHIPPER
442346889 PLEW     SHIPPER
213764555 GLASS    SHIPPER
313782439 GLASS    SHIPPER
220984332 WALLACE  SHIPPER

30 rows selected.

You may be curious why 30 rows were retrieved when only 6 rows exist in each table. For every record in EMPLOYEE_TBL, there is a corresponding record in EMPLOYEE_PAY_TBL. Because non-equality was tested in the join of the two tables, each row in the first table is paired with all rows from the second table, except for its own corresponding row. This means that each of the 6 rows are paired with 5 unrelated rows in the second table; 6 rows multiplied by 5 rows equals 30 rows total.

In the previous section's test for equality example, each of the six rows in the first table were paired with only one row in the second table (each row's corresponding row); six rows multiplied by one row yields a total of six rows.

Outer Joins

An OUTER JOIN is used to return all rows that exist in one table, even though corresponding rows do not exist in the joined table. The (+) symbol is used to denote an OUTER JOIN in a query. The (+) is placed at the end of the table name in the WHERE clause. The table with the (+) should be the table that does not have matching rows. In many implementations, the OUTER JOIN is broken down into joins called LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN. The OUTER JOIN in these implementations is normally optional.

The general syntax is

   syntax_icon.gif
FROM TABLE1
{RIGHT | LEFT | FULL} [OUTER] JOIN
ON TABLE2

The Oracle syntax is

FROM TABLE1, TABLE2 [, TABLE3 ] 
WHERE TABLE1.COLUMN_NAME[(+)] = TABLE2.COLUMN_NAME[(+)]
[ AND TABLE1.COLUMN_NAME[(+)] = TABLE3.COLUMN_NAME[(+)]]

The concept of the OUTER JOIN is explained in the next two examples. In the first example, the product description and the quantity ordered are selected; both values are extracted from two separate tables. One important factor to keep in mind is that there may not be a corresponding record in the ORDERS_TBL table for every product. A regular join of equality is performed:

   input_icon.gif

   SELECT P.PROD_DESC, O.QTY

   FROM PRODUCTS_TBL P,
     
   ORDERS_TBL O

   WHERE P.PROD_ID = O.PROD_ID;

   output_icon.gif
PROD_DESC                        QTY
-------------------------------- ---
WITCHES COSTUME                    1
PLASTIC PUMPKIN 18 INCH           25
PLASTIC PUMPKIN 18 INCH            2
LIGHTED LANTERNS                  10
FALSE PARAFFIN TEETH              20
KEY CHAIN                          1

6 rows selected.

Only six rows were selected, but there are 10 distinct products. You want to display all products, whether the products have been placed on order or not.

The next example accomplishes the desired output through the use of an OUTER JOIN. Oracle's syntax is used for the OUTER JOIN.

   mysql_icon.gif
   input_icon.gif

   SELECT P.PROD_DESC, O.QTY

   FROM PRODUCTS_TBL P,
     
   ORDERS_TBL O

   WHERE P.PROD_ID = O.PROD_ID(+);


   output_icon.gif
PROD_DESC                        QTY
-------------------------------- ---
WITCHES COSTUME                    1
ASSORTED MASKS
FALSE PARAFFIN TEETH              20
ASSORTED COSTUMES
PLASTIC PUMPKIN 18 INCH           25
PLASTIC PUMPKIN 18 INCH            2
PUMPKIN CANDY
PLASTIC SPIDERS
CANDY CORN
LIGHTED LANTERNS                  10
KEY CHAIN                          1
OAK BOOKSHELF

12 rows selected.

All products were returned by the query, even though they may not have had a quantity ordered. The outer join is inclusive of all rows of data in the PRODUCTS_TBL table, whether a corresponding row exists in the ORDERS_TBL table or not.

Self Joins

The SELF JOIN is used to join a table to itself, as if the table were two tables, temporarily renaming at least one table in the SQL statement. The syntax is as follows:

   syntax_icon.gif
SELECT A.COLUMN_NAME, B.COLUMN_NAME, [ C.COLUMN_NAME ]
FROM TABLE1 A, TABLE2 B [, TABLE3 C ]
WHERE A.COLUMN_NAME = B.COLUMN_NAME
[ AND A.COLUMN_NAME = C.COLUMN_NAME ]

The following is an example:

SELECT A.LAST_NAME, B.LAST_NAME, A.FIRST_NAME 
FROM EMPLOYEE_TBL A,
     EMPLOYEE_TBL B
WHERE A.LAST_NAME = B.LAST_NAME;

analysis_icon.gif

The preceding SQL statement returns the employees' first name for all the employees with the same last name from the EMPLOYEE_TBL. Self joins are useful when all of the data you want to retrieve resides in one table, but you must somehow compare records in the table to other records in the table.

Another common example used to explain a self join is as follows. Suppose you have a table that stores an employee identification number, the employee's name, and the employee identification number of the employee's manager. You may want to produce a list of all employees and their managers' names. The problem is that the manager name does not exist in the table, only the employee name:

SELECT * FROM EMP; 

ID   NAME      MGR_ID
---- --------- ------
1    JOHN      0
2    MARY      1
3    STEVE     1
4    JACK      2
5    SUE       2

In the following example, we have included the table EMP twice in the FROM clause of the query, giving the table two aliases for the purpose of the query. By providing two aliases, it is as if you are selecting from two distinct tables. All managers are also employees, so the join condition between the two tables compares the value of the employee identification number from the first table with the manager identification number in the second table. The first table acts as a table that stores employee information, whereas the second table acts as a table that stores manager information:

SELECT E1.NAME, E2.NAME 
FROM EMP E1, EMP E2
WHERE E1.MGR_ID = E2.ID;

NAME      NAME
--------- ---------
MARY      JOHN
STEVE     JOHN
JACK      MARY
SUE       MARY

Joining on Multiple Keys

Most join operations involve the merging of data based on a key in one table and a key in another table. Depending on how your database has been designed, you may have to join on more than one key field to accurately depict that data in your database. You may have a table that has a primary key that is comprised of more than one column. You may also have a foreign key in a table that consists of more than one column, which references the multiple column primary key.

Consider the following Oracle tables that are used here for examples only:

SQL> desc prod 
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 SERIAL_NUMBER                             NOT NULL NUMBER(10)
 VENDOR_NUMBER                             NOT NULL NUMBER(10)
 PRODUCT_NAME                              NOT NULL VARCHAR2(30)
 COST                                      NOT NULL NUMBER(8,2)

SQL> desc ord
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ORD_NO                                    NOT NULL NUMBER(10)
 PROD_NUMBER                               NOT NULL NUMBER(10)
 VENDOR_NUMBER                             NOT NULL NUMBER(10)
 QUANTITY                                  NOT NULL NUMBER(5)
 ORD_DATE                                  NOT NULL DATE

The primary key in PROD is the combination of the columns SERIAL_NUMBER and VENDOR_NUMBER. Perhaps two products can have the same serial number within the distribution company, but each serial number is unique per vendor.

The foreign key in ORD is also the combination of the columns SERIAL_NUMBER and VENDOR_NUMBER.

When selecting data from both tables (PROD and ORD), the join operation may appear as follows:

SELECT P.PRODUCT_NAME, O.ORD_DATE, O.QUANTITY 
FROM PROD P, ORD O
WHERE P.SERIAL_NUMBER = O.SERIAL_NUMBER
  AND P.VENDOR_NUMBER = O.VENDOR_NUMBER;

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On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020