Sams Teach Yourself SQL in 24 Hours
- Table of Contents
- Copyright
- About the Authors
- Acknowledgments
- Tell Us What You Think!
- Introduction
- Part I: A SQL Concepts Overview
- Hour 1. Welcome to the World of SQL
- Part II: Building Your Database
- Hour 2. Defining Data Structures
- Hour 3. Managing Database Objects
- Hour 4. The Normalization Process
- Hour 5. Manipulating Data
- Hour 6. Managing Database Transactions
- Part III: Getting Effective Results from Queries
- Hour 7. Introduction to the Database Query
- Hour 8. Using Operators to Categorize Data
- Hour 9. Summarizing Data Results from a Query
- Hour 10. Sorting and Grouping Data
- Hour 11. Restructuring the Appearance of Data
- Hour 12. Understanding Dates and Times
- Part IV: Building Sophisticated Database Queries
- Hour 13. Joining Tables in Queries
- Hour 14. Using Subqueries to Define Unknown Data
- Hour 15. Combining Multiple Queries into One
- Part V: SQL Performance Tuning
- Hour 16. Using Indexes to Improve Performance
- Hour 17. Improving Database Performance
- Part VI: Using SQL to Manage Users and Security
- Hour 18. Managing Database Users
- Hour 19. Managing Database Security
- Part VII: Summarized Data Structures
- Hour 20. Creating and Using Views and Synonyms
- Hour 21. Working with the System Catalog
- Part VIII: Applying SQL Fundamentals in Today's World
- Hour 22. Advanced SQL Topics
- Hour 23. Extending SQL to the Enterprise, the Internet, and the Intranet
- Hour 24. Extensions to Standard SQL
- Part IX: Appendixes
- Appendix A. Common SQL Commands
- Appendix B. Using MySQL for Exercises
- Appendix C. Answers to Quizzes and Exercises
- Appendix D. CREATE TABLE Statements for Book Examples
- Appendix E. INSERT Statements for Data in Book Examples
- Appendix F. Glossary
- Appendix G. Bonus Exercises
Using an ORDER BY with a Compound Query
The ORDER BY clause can be used with a compound query. However, the ORDER BY can only be used to order the results of both queries. Therefore, there can be only one ORDER BY clause in a compound query, even though the compound query may consist of multiple individual queries or SELECT statements. The ORDER BY must reference the columns being ordered by an alias or by the number of column order.
The syntax is as follows:
SELECT COLUMN1 [, COLUMN2 ] FROM TABLE1 [, TABLE2 ] [ WHERE ] OPERATOR{UNION | EXCEPT | INTERSECT | UNION ALL} SELECT COLUMN1 [, COLUMN2 ] FROM TABLE1 [, TABLE2 ] [ WHERE ] [ ORDER BY ]
Examine the following example:
SELECT EMP_ID FROM EMPLOYEE_TBL UNION SELECT EMP_ID FROM EMPLOYEE_PAY_TBL ORDER BY 1;
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The results of the compound query are sorted by the first column of each individual query. Duplicate records can easily be recognized by sorting compound queries. |
The preceding SQL statement returns the employee ID from the EMPLOYEE_TBL and the EMPLOYEE_PAY_TBL, but does not show duplicates and orders by the employee ID.
The following example shows the use of the ORDER BY clause with a compound query. The column name can be used in the ORDER BY clause if the column sorted by has the same name in all individual queries of the statement.
SELECT PROD_DESC FROM PRODUCTS_TBL UNION SELECT PROD_DESC FROM PRODUCTS_TBL ORDER BY PROD_DESC;
PROD_DESC ----------------------- ASSORTED COSTUMES ASSORTED MASKS CANDY CORN FALSE PARAFFIN TEETH KEY CHAIN LIGHTED LANTERNS OAK BOOKSHELF PLASTIC PUMPKIN 18 INCH PLASTIC SPIDERS PUMPKIN CANDY WITCHES COSTUME 11 rows selected.
The following query uses a numeric value in place of the actual column name in the ORDER BY clause:
Using GROUP BY with a Compound Query | Next Section
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