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SQL and XQuery tutorial for IBM DB2, Part 2: Basic queries

The fundamentals of SQL queries

Pat Moffatt (pmoffatt@ca.ibm.com), Information Management Program Manager, IBM Academic Initiative, IBM
Pat Moffatt is the Information Management Program Manager for the IBM Academic Initiative. Through the Academic Initiative program, she ensures that appropriate Information Management resources are made available to help faculty integrate Information Management software into their curriculum. To learn more about this program, visit www.ibm.com/university/data.
Bruce Creighton (bcreight@ca.ibm.com), Skills Segment Planner, IBM
Bruce Creighton is a Skills Segment Planner in the Information Management Education Planning and Development department. In this role, he plans investment in educational content and balances the investment between areas where IBM can attain revenue and those where the requirement for skills development are important enough to provide free education.
Jessica Cao, Training Tools Developer, IBM
Jessica Cao is an Arts and Science and Computer Science student at McMaster University. She expects to complete her combined honours degree in April 2009. Jessica is working in IBM Toronto lab's DB2 Information Management Skills Channel Planning and Enablement Program to take advantage of her interest in programming, editing, and writing.

Summary:  Through a series of simple examples, this tutorial illustrates how to retrieve data from an IBM® DB2® database with standard SQL SELECT statements. This tutorial describes how to retrieve rows from a relational database table, retrieve specific columns, retrieve specific rows, reform logical operations on retrieved data, and use wildcard characters in search conditions. This tutorial is Part 2 of the SQL & XQuery tutorial for IBM DB2 series.

View more content in this series

Date:  03 Aug 2006
Level:  Introductory PDF:  A4 and Letter (97 KB | 25 pages)Get Adobe® Reader®

Activity:  39943 views
Comments:  

Using SELECT list to retrieve specific columns

Question

Which districts and regions are defined in the Aroma database?

Example query

		SELECT district, region
		FROM aroma.market;

Result

DistrictRegion
AtlantaSouth
AtlantaSouth
New OrleansSouth
New OrleansSouth
New YorkNorth
New YorkNorth
BostonNorth
BostonNorth
ChicagoCentral
ChicagoCentral
MinneapolisCentral
MinneapolisCentral
San FranciscoWest
San FranciscoWest
San FranciscoWest
Los AngelesWest
Los AngelesWest


Retrieving specific columns

By naming the columns in the SELECT list of a SELECT statement, you can retrieve a specific set of columns from any table. Columns are returned in the order you specify in the SELECT list.

About the query

The example query requests a list of districts and their corresponding regions from the Market table.

Usage notes

Although column names in the SELECT list must be defined in the tables referenced in the FROM clause, other expressions can also occur in the SELECT list. Several examples of such expressions are discussed later in this series.

When the SELECT list does not include all the columns in a table, a query might return duplicate rows, as in the previous example query. You can eliminate the duplicates by using the DISTINCT keyword. For example, the following query returns only the names of distinct districts and regions in the Market table:

		SELECT DISTINCT district, region
		FROM aroma.market;

DistrictRegion
ChicagoCentral
MinneapolisCentral
BostonNorth
New YorkNorth
AtlantaSouth
New OrleansSouth
Los AngelesWest
San FranciscoWest

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