Application Programming and SQL Guide - Kmlinux

With a single SELECT statement, you can select data from one column or as many
as 750 columns.
Selecting derived columns: SELECT expression
You can select columns derived from a constant, an expression, or a function.
Example: SELECT with an expression: This SQL statement generates a result
table in which the second column is a derived column that is generated by adding
the values of the SALARY, BONUS, and COMM columns.
SELECT EMPNO, (SALARY + BONUS + COMM)
FROM DSN8810.EMP;
Derived columns in a result table, such as (SALARY + BONUS + COMM), do not
have names. You can use the AS clause to give a name to an unnamed column of
the result table. For information about using the AS clause, see “Naming result
columns: AS.”
To order the rows in a result table by the values in a derived column, specify a
name for the column by using the AS clause, and specify that name in the ORDER
BY clause. For information about using the ORDER BY clause, see “Putting the
rows in order: ORDER BY” on page 9.
Eliminating duplicate rows: DISTINCT
The DISTINCT keyword removes duplicate rows from your result table, so that each
row contains unique data.
Example: SELECT DISTINCT: The following SELECT statement lists unique
department numbers for administrating departments:
SELECT DISTINCT ADMRDEPT
FROM DSN8810.DEPT;
The result table looks similar to the following output:
ADMRDEPT
========
A00
D01
E01
Naming result columns: AS
With the AS clause, you can name result columns in a SELECT statement. This is
particularly useful for a column that is derived from an expression or a function. For
syntax and more information about the AS clause, see Chapter 4 of DB2 SQL
Reference.
The following examples show different ways to use the AS clause.
Example: SELECT with AS CLAUSE: The following example of the SELECT
statement gives the expression SALARY+BONUS+COMM the name TOTAL_SAL.
SELECT SALARY+BONUS+COMM AS TOTAL_SAL
FROM DSN8810.EMP
ORDER BY TOTAL_SAL;
Example: CREATE VIEW with AS clause: You can specify result column names in
the select-clause of a CREATE VIEW statement. You do not need to supply the
Chapter 1. Retrieving data 7