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OPP 2007February 28 March 1, 2007
San Mateo Marriott
San Mateo, California
An ODTUG SP* Oracle PL/SQLProgramming Conference
*SP Seriously Practical Conference
For more information visit www.odtug.com or call 910-452-7444
ODTUG KaleidoscopeJune 18 21, 2007
Pre-conference Hands-on Training - June 16 17
Hilton Daytona Beach Oceanfront Resort
Daytona, Florida
WOW-Wide Open World, Wide Open Web!
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Everything you need to know
about collections,but were afraid to ask
Steven FeuersteinPL/SQL Evangelist
Quest Software
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Ten Years Writing Ten Bookson the Oracle PL/SQL Language
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How to benefit most from this seminar
Watch, listen, ask questions.
Download the training materials and supporting scripts: http://oracleplsqlprogramming.com/resources.html
"Demo zip": all the scripts I run in my class available at
http://oracleplsqlprogramming.com/downloads/demo.zip
Use these materials as an accelerator as you venture intonew territory and need to apply new techniques.
Play games! Keep your brain fresh and active by mixinghard work with challenging games
MasterMind and Set (www.setgame.com)
filename_from_demo_zip.sql
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PL/SQL Collections
Collections are single-dimensionedlists ofinformation, similar to 3GL arrays.
They are an invaluable data structure.
AllPL/SQL developers should be very comfortablewith collections and use them often.
Collections take some getting used to.
They are not the most straightforward
implementation of array-like structures. Advanced features like string indexes and multi-
level collections can be a challenge.
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What we will cover on collections
Review of basic functionality
Indexing collections by strings
Working with collections of collections MULTISET operators for nested tables
Then later in the section on SQL:
Bulk processing with FORALL and BULK
COLLECT
Table functions and pipelined functions
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What is a collection?
A collection is an "ordered group of elements,
all of the same type." (PL/SQL User Guide andReference) That's a very general definition; lists, sets, arrays and
similar data structures are all types of collections.
Each element of a collection may be addressed by a unique
subscript, usually an integer but in some cases also a string. Collections are single-dimensional, but you can create
collections of collections to emulate multi-dimensionalstructures.
abc def sf q rrr swq ...1 2 3 4 22 23
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Why use collections?
Generally, to manipulate in-program-memory lists of
information.
Much faster than working through SQL.
Serve up complex datasets of information to non-PL/SQL host environments using table functions.
Dramatically improve multi-row querying, inserting,
updating and deleting the contents of tables.
Combined with BULK COLLE
CT and FORALL.... Emulate bi-directional cursors, which are not yet
supported within PL/SQL.
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Three Types of Collections
Associative arrays (aka index-by tables)
Can be used only in PL/SQL blocks.
Similar to hash tables in other languages, allows you to
access elements via arbitrary subscript values. Nested tables and Varrays
Can be used in PL/SQL blocks, but also can be the
datatype of a column in a relational table.
Part of the object model in PL/SQL.
Required for some features, such as table functions
With Varrays, you specify a maximum number of elements
in the collection, at time of definition.
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About Associative Arrays
Unbounded, practically speaking.
Valid row numbers range from -2,147,483,647 to
2,147,483,647.
This range allows you to employ the row number as anintelligent key, such as the primary key or unique index
value, because AAs also are:
Sparse
Data does not have to be stored in consecutive rows, as isrequired in traditional 3GL arrays and VARRAYs.
Index values can be integers or strings (Oracle9i R2
and above).assoc_array_example.sql
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About Nested Tables
No pre-defined limit on a nested table.
Valid row numbers range from 1 to
2,147,483,647.
Part of object model, requiring initialization.
Is always dense initially, but can become
sparse after deletes.
Can be defined as a schema level type and
used as a relational table column type.
nested_table_example.sql
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About Varrays
Has a maximum size, associated with its type.
Can adjust the size at runtime in Oracle10g R2.
Part of object model, requiring initialization. Is always dense; you can only remove
elements from the end of a varray.
Can be defined as a schema level type andused as a relational table column type.
varray_example.sql
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How to choose your collection type
Use associative arrays when you need to... Work within PL/SQL code only
Sparsely fill and manipulate the collection
Take advantage of negative index values
Use nested tables when you need to... Access the collection inside SQL (table functions, columns in
tables)
Want to perform set operations
Use varrays when you need to... If you need to specify a maximum size to your collection
Access the collection inside SQL (table functions, columns intables).
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Wide Variety of Collection Methods
Obtain information about the collection COUNT returns number of rows currently defined in
collection.
EXISTS returns TRUE if the specified row is defined.
FIRST/LAST return lowest/highest numbers of defined rows. NEXT/PRIOR return the closest defined row after/before the
specified row.
LIMIT tells you the max. number of elements allowed in aVARRAY.
Modify the contents of the collection DELETE deletes one or more rows from the index-by table.
EXTEND adds rows to a nested table or VARRAY.
TRIM removes rows from a VARRAY.
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Useful reminders for PL/SQL collections
Memory for collections comes out of the PGA orProcess Global Area One per session, so a program using collections can
consume a large amount of memory.
Use the NOCOPY hint to reduce overhead of passingcollections in and out of program units.
Encapsulate or hide details of collection management.
Don't always fill collections sequentially. Think about
how you need to manipulate the contents. Try to read a row that doesn't exist, and Oracle raises
NO_DATA_FOUND.mysess.pkg
sess2.sql
nocopy*.*
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FunctionPGA
Data Caching with PL/SQL Tables
First access
Subsequent accesses
PGAFunction
Database
Not in cache;
Request data
from database
Pass Data
to Cache
Application
Application
Requests Data
Data retrievedfrom cache Data returned
to application
Application
Application
Requests Data
Data returned
to application
Data retrieved
from cache
Database
Data found in
cache. Database
is not needed.
emplu.pkg
emplu.tst
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New indexing capabilitiesfor associative arrays
Prior to Oracle9iR2, you could only index byBINARY_INTEGER.
You can now define the index on your associative
array to be: Any sub-type derived from BINARY_INTEGER VARCHAR2(n), where n is between 1 and 32767
%TYPE against a database column that is consistent withthe above rules
A SUBTYPE against any of the above. This means that you can now index on string
values! (and concatenated indexes and...)
Oracle9iRelease 2
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Examples of NewTYPE Variants
All of the following are now valid TYPE declarations inOracle9i Release 2 You cannot use %TYPE against an INTEGER column,
because INTEGER is nota subtype of BINARY_INTEGER.
DECLARE
TYPE array_t1 IS TABLE OF NUMBER INDEX BY BINARY_INTEGER;TYPE array_t2 IS TABLE OF NUMBER INDEX BY PLS_INTEGER;TYPE array_t3 IS TABLE OF NUMBER INDEX BY POSITIVE;TYPE array_t4 IS TABLE OF NUMBER INDEX BY NATURAL;TYPE
array_t5IS TABLE OF NUMBER INDEX BY VARCHAR
2(64);
TYPE array_t6 IS TABLE OF NUMBER INDEX BY VARCHAR2(32767);TYPE array_t7 IS TABLE OF NUMBER INDEX BY
employee.last_name%TYPE;TYPE array_t8 IS TABLE OF NUMBER INDEX BY
types_pkg.subtype_t;
Oracle9iRelease 2
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Working with string-indexed collections
Specifying a row via a string takes some gettingused to, but if offers some very powerful advantages.
DECLARE
TYPE population_type IS TABLE OF NUMBER INDEX BY VARCHAR2(64);
country_populationpopulation_type;continent_populationpopulation_type;
howmany NUMBER;BEGIN
country_population('Greenland') := 100000;country_population('Iceland') := 750000;
howmany := country_population('Greenland');
continent_population('Australia') := 30000000;END;
assoc_array*.sql
assoc_array_perf.tst
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Multi-level Collections
Prior to Oracle9i, you could have collections ofrecords or objects, but only if all fields werescalars.
A collection containing another collection was notallowed.
Now you can create collections that containother collections and complex types.
Applies to all three types of collections.
The syntax is non-intuitive and resulting codecan be quite complex.
Oracle9i
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String Tracker Version 2
The problem with String Tracker V1 is that it
only supports a single list of strings.
What if I need to track multiple lists
simultaneously or nested?
Let's extend the first version to support
multiple lists by using a string-indexed, multi-
level collection. A list of lists....
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The String Tracker package (V2)
CREATE OR REPLACE PACKAGE BODY string_trackerIS
TYPE used_aat IS TABLE OF BOOLEAN INDEX BY maxvarchar2_t;TYPE list_of_lists_aat IS TABLE OF used_aat INDEX BY maxvarchar2_t;g_list_of_listslist_of_lists_aat;
PROCEDURE mark_as_used(
list_in IN maxvarchar2_t,value_in IN maxvarchar2_t,case_sensitive_in IN BOOLEAN DEFAULT FALSE
) ISl_namemaxvarchar2_t :=
CASE case_sensitive_in WHEN TRUE THEN value_inELSE UPPER(value_in) END;
BEGINg_list_of_lists(list_in)(l_name) := TRUE;
END mark_as_used;END string_tracker;
string_tracker2.*
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Encapsulate these complex structures!
When working with multi-level collections, youcan easily and rapidly arrive at completelyunreadable and un-maintainable code.
What' s a developer to do? Hide complexity -- and all data structures -- behind
small modules.
Work with and through functions to retrieve
contents and procedures to set contents.
cc_smartargs.pkb:
cc_smartargs.next_overloading
cc_smartargs.add_new_parameter
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Nested Tables unveil theirMULTISET-edness
Oracle10g introduces high-level set operations
on nested tables (only).
Nested tables are multisets, meaning that
theoretically there is no order to their elements. Thismakes set operations of critical importance for
manipulating nested tables. .
You can now
Check for equality and inequality
Perform UNION, INTERSECT and MINUS operations
Check for and remove duplicates
Oracle10g
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Check for equality and inequality
Just use the basic operators.
Oracle10g
DECLARE
TYPE clientele IS TABLE OF VARCHAR2(64);group1 clientele := clientele('Customer1','Customer2');group2 clientele := clientele('Customer1','Customer3');group3 clientele := clientele('Customer3','Customer1');
BEGIN
IF group1 = group2 THENDBMS_OUTPUT.put_line('Group1 = Group2');
ELSE
DBMS_OUTPUT.put_line('Group1 != Group2');END IF;
IF group2 != group3 THEN
DBMS_OUTPUT.put_line('Group2 != Group3');ELSE
DBMS_OUTPUT.put_line('Group2 = Group3');END IF;
END;
10g_compare.sql
10g_compare2.sql
10g_compare_old.sql
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UNION, INTERSECT, MINUS
Straightforward, with the MULTISET keyword.
Oracle10g
BEGIN
our_favorites := my_favorites MULTISET UNION dad_favorites;show_favorites('MINE then DAD',our_favorites);
our_favorites := dad_favorites MULTISET UNION my_favorites;show_favorites('DAD then MINE',our_favorites);
our_favorites := my_favorites MULTISET UNION DISTINCT dad_favorites;show_favorites('MINE then DAD with DISTINCT',our_favorites);
our_favorites := my_favorites MULTISET INTERSECT dad_favorites;show_favorites('IN COMMON',our_favorites);
our_favorites := dad_favorites MULTISET EXCEPT my_favorites;show_favorites('ONLY DAD''S',our_favorites);
END;
10g_setops.sql
10g_string_nt.sql
10g_favorites.sql
10g*union*.sql
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Turbo-charged SQL withBULK COLLECT and FORALL
Improve the performance of multi-row SQL
operations by an order of magnitude or more
with bulk/array processing in PL/SQL!
CREATE OR REPLACE PROCEDURE upd_for_dept(dept_in IN employee.department_id%TYPE
,newsal_in IN employee.salary%TYPE)IS
CURSORemp_cur ISSELECT employee_id,salary,hire_dateFROMemployee WHERE department_id = dept_in;
BEGIN
FORrec IN emp_cur LOOPUPDATE employee SET salary = newsal_inWHERE employee_id = rec.employee_id;
END LOOP;
END upd_for_dept;
Conventional
binds (and
lots of them!)
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Oracle server
PL/SQLRuntime Engine SQL Engine
PL/SQL blockProcedural
statementexecutorSQL
statement
executor
FORrec IN emp_cur LOOPUPDATE employee
SET salary = ...WHERE employee_id =
rec.employee_id;END LOOP;
Performance penaltyPerformance penaltyfor many contextfor many context
switchesswitches
Conventional Bind
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Enter the Bulk Bind: FORALL
Oracle server
PL/SQLRuntime Engine SQL Engine
PL/SQL blockProcedural
statementexecutorSQL
statement
executor
FORALL indx INlist_of_emps.FIRST..list_of_emps.LAST
UPDATE employeeSET salary = ...
WHERE employee_id =list_of_emps(indx);
Much less overhead for
Much less overhead forcontext switchingcontext switching
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Use the FORALL Bulk Bind Statement
Instead of executing repetitive, individual DMLstatements, you can write your code like this:
Things to be aware of: You MUST know how to use collections to use this feature!
Only a single DML statement is allowed per FORALL. New cursor attributes: SQL%BULK_ROWCOUNT returns number of
rows affected by each row in array. SQL%BULK_EXCEPTIONS...
Prior to Oracle10g, the binding arraymust be sequentially filled.
Use SAVEEXCEPTIONS to continue past errors.
PROCEDURE upd_for_dept(...) ISBEGIN
FORALL indx IN list_of_emps.FIRST ..list_of_emps.LASTUPDATE employee
SET salary = newsal_inWHERE employee_id = list_of_emps(indx);
END;
bulktiming.sql
bulk_rowcount.sql
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Use BULK COLLECT INTO for Queries
DECLARE
TYPE employees_aat IS TABLE OF employees%ROWTYPEINDEX BY BINARY_INTEGER;
l_employeesemployees_aat;BEGIN
SELECT *BULK COLLECT INTO l_employeesFROMemployees;
FORindx IN 1..l_employees.COUNTLOOP
process_employee(l_employees(indx));END LOOP;
END;
bulkcoll.sql
Declare a
collection of
records to hold
the queried data.
Use BULK
COLLECT to
retrieve all rows.
Iterate through thecollection
contents with a
loop.
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Limit the number of rows returned byBULK COLLECT
CREATE OR REPLACE PROCEDURE bulk_with_limit(deptno_in IN dept.deptno%TYPE)
IS
CURSORemps_in_dept_cur ISSELECT *
FROMempWHERE deptno = deptno_in;
TYPE emp_tt IS TABLE OF emps_in_dept_cur%ROWTYPE;empsemp_tt;
BEGIN
OPEN emps_in_dept_cur;LOOP
FETCH emps_in_dept_curBULK COLLECT INTO empsLIMIT
100;
EXIT WHEN emps.COUNT = 0;
process_emps(emps);END LOOP;
END bulk_with_limit;
Use the LIMIT clause with the
INTO to manage the amount
of memory used with the
BULK COLLECT operation.
WARNING!
BULK COLLECT will notraise
NO_DATA_FOUND if no rows
are found.
Best to check contents of
collection to confirm that
something was retrieved.bulklimit.sql
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Tips and Fine Points
Use bulk binds in these circumstances: Recurring SQL statement in PL/SQL loop. Oracle
recommended threshold: five rows!
Bulk bind rules:
Can be used with any kind of collection; Collectionsubscripts cannot be expressions; The collectionsmust be densely filled (pre-10gR2).
Bulk collects:
Can be used with implicit and explicit cursors
Collection is always filled sequentially, starting atrow 1.
emplu.pkg
cfl_to_bulk*.*
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The Wonder Of Table Functions
A table function is a function that you can call in theFROM clause of a query, and have it be treated as if itwere a relational table.
Table functions allow you to perform arbitrarily
complex transformations of data and then make thatdata available through a query. Not everything can be done in SQL.
Combined with REF CURSORs, you can now more
easily transfer data from within PL/SQL to hostenvironments. Java, for example, works very smoothly with cursor
variables
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Building a table function
A table function must return a nested table orvarray based on a schema-defined type, ortype defined in a PL/SQL package.
The function header and the way it is calledmust be SQL-compatible: all parameters useSQL types; no named notation.
In some cases (streaming and pipelined
functions), the IN parameter must be a cursorvariable -- a query result set.
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Simple table function example
Return a list of names as a nested table, and
then call that function in the FROM clause.
CREATE OR REPLACE FUNCTION lotsa_names(base_name_in IN VARCHAR2,count_in IN INTEGER
)RETURN names_nt
IS
retval names_nt := names_nt();BEGIN
retval.EXTEND (count_in);
FORindx IN 1..count_in
LOOPretval(indx) :=
base_name_in || '' || indx;END LOOP;
RETURN retval;END lotsa_names; tabfunc_scalar.sql
SELECT column_valueFROM TABLE (
lotsa_names('Steven',100))names;
COLUMN_VALUE------------
Steven1...Steven100
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Streaming data with table functions
You can use table functions to "stream" data
through several stages within a single SQL
statement.
Example: transform one row in the stocktable to tworows in the tickertable. CREATE TABLE stocktable(
ticker VARCHAR2(20),trade_date DATE,open_price NUMBER,close_price NUMBER
)/CREATE TABLE tickertable(
ticker VARCHAR2(20),pricedate DATE,pricetype VARCHAR2(1),price NUMBER)
/
tabfunc_streaming.sql
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Streaming data with table functions - 2
In this example, transform each row of the
stocktable into two rows in the tickertable.
CREATE OR REPLACE PACKAGE refcur_pkgIS
TYPE refcur_t IS REF CURSORRETURN stocktable%ROWTYPE;
END refcur_pkg;/
CREATE OR REPLACE FUNCTION stockpivot(datasetrefcur_pkg.refcur_t)RETURN tickertypeset...
BEGIN
INSERT INTO tickertableSELECT *
FROM TABLE (stockpivot(CURSOR(SELECT *FROMstocktable)));
END;
/
tabfunc_streaming.sql
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Use pipelined functions to enhanceperformance.
Pipelined functions allow you to return data
iteratively, asynchronous to termination of the
function. As data is produced within the function, it is
passed back to the calling process/query.
Pipelined functions can be defined to supportparallel execution.
Iterative data processing allows multiple
processes to work on that data simultaneously.
CREATE FUNCTION StockPivot(prefcur_pkg.refcur_t)RETURN TickerTypeSetPIPELINED
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Applications for pipelined functions
Execution functions in parallel.
In Oracle9i Database Release 2 and above, use thePARALLEL_ENABLE clause to allow your pipelined
function to participate fully in a parallelized query. Critical in data warehouse applications.
Improve speed of delivery of data to webpages.
Use a pipelined function to "serve up" data to thewebpage and allow users to being viewing andbrowsing, even before the function has finishedretrieving all of the data.
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Piping rows out from a pipelined function
CREATE FUNCTION stockpivot(prefcur_pkg.refcur_t)RETURN tickertypesetPIPELINED
IS
out_rec tickertype :=tickertype(NULL, NULL, NULL);
in_rec p%ROWTYPE;
BEGINLOOP
FETCH p INTO in_rec;EXIT WHEN p%NOTFOUND;out_rec.ticker := in_rec.ticker;out_rec.pricetype := 'O';out_rec.price := in_rec.openprice;
PIPE ROW(out_rec);
END LOOP;CLOSE p;
RETURN;
END;
tabfunc_setup.sql
tabfunc_pipelined.sql
Add PIPELINED
keyword to header
Pipe a row of data
back to calling block
or query
RETURN...nothing at
all!
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Enabling Parallel Execution
The table function's parameter list must consist only
of a single strongly-typedREF CURSOR.
Include the PARALLEL_ENABLE hint in the program
header. Choose a partition option that specifies how the function's
execution should be partitioned.
"ANY" means that the results are independent of the order
in which the function receives the input rows (through the
REF CURSOR).
{[ORDER | CLUSTER] BY column_list}
PARALLEL_ENABLE ({PARTITION p BY[ANY | (HASH | RANGE)column_list]} )
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Table functions Summary
Table functions offer significant new flexibility
for PL/SQL developers.
Consider using them when you...
Need to pass back complex result sets of data
through the SQL layer (a query);
Want to call a user defined function inside a
query and execute it as part of a parallel query.
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Collections don't start coding without them.
It is impossible to write modern PL/SQL code,
taking full advantage of new features, unless you
use collections.
From array processing to table functions, collections arerequired.
Today I offer this challenge: learn collections
thoroughly and apply them throughout your
backend code.
Your code will get faster and in many cases much
simpler than it might have been (though not always!).
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OPP 2007February 28 March 1, 2007
San Mateo Marriott
San Mateo, California
An ODTUG SP* Oracle PL/SQL
Programming Conference
*SP Seriously Practical Conference
For more information visit www.odtug.com or call 910-452-7444
ODTUG KaleidoscopeJune 18 21, 2007
Pre-conference Hands-on Training - June 16 17Hilton Daytona Beach Oceanfront Resort
Daytona, Florida
WOW-Wide Open World, Wide Open Web!