Application Programming and SQL Guide - Kmlinux

ows to be deleted from the table at a commit point, unless there is a held cursor
open on the table at the commit point. ON COMMIT PRESERVE ROWS causes the
rows to remain past the commit point.
Example: Suppose that you run the following statement in an application program:
EXEC SQL DECLARE GLOBAL TEMPORARY TABLE TEMPPROD
AS (SELECT * FROM BASEPROD)
DEFINITION ONLY
INCLUDING IDENTITY COLUMN ATTRIBUTES
INCLUDING COLUMN DEFAULTS
ON COMMIT PRESERVE ROWS;
EXEC
.
SQL INSERT INTO SESSION.TEMPPROD SELECT * FROM BASEPROD;
.
EXEC
.
SQL COMMIT;
.
When DB2 runs the preceding DECLARE GLOBAL TEMPORARY TABLE
statement, DB2 creates an empty instance of TEMPPROD. The INSERT statement
populates that instance with rows from table BASEPROD. The qualifier, SESSION,
must be specified in any statement that references TEMPPROD. When DB2
executes the COMMIT statement, DB2 keeps all rows in TEMPPROD because
TEMPPROD is defined with ON COMMIT PRESERVE ROWS. When the program
ends, DB2 drops TEMPPROD.
Dropping tables: DROP TABLE
The following SQL statement drops the YEMP table:
Working with views
DROP TABLE YEMP;
Use the DROP TABLE statement with care: Dropping a table is NOT equivalent
to deleting all its rows. When you drop a table, you lose more than its data and its
definition. You lose all synonyms, views, indexes, and referential and check
constraints associated with that table. You also lose all authorities granted on the
table.
For more information about the DROP statement, see Chapter 5 of DB2 SQL
Reference.
This section discusses how to use CREATE VIEW and DROP VIEW to control your
views of existing tables. Although you cannot modify an existing view, you can drop
it and create a new one if your base tables change in a way that affects the view.
Dropping and creating views does not affect the base tables or their data.
Defining a view: CREATE VIEW
A view does not contain data; it is a stored definition of a set of rows and columns.
A view can present any or all of the data in one or more tables and, in most cases,
is interchangeable with a table. Using views can simplify writing SQL statements.
Use the CREATE VIEW statement to define a view and give the view a name, just
as you do for a table. The view created with the following statement shows each
department manager’s name with the department data in the DSN8810.DEPT table.
CREATE VIEW VDEPTM AS
SELECT DEPTNO, MGRNO, LASTNAME, ADMRDEPT
FROM DSN8810.DEPT, DSN8810.EMP
WHERE DSN8810.EMP.EMPNO = DSN8810.DEPT.MGRNO;
Chapter 2. Working with tables and modifying data 25