Re: Using host variable in embedded sql -- RPG400-L

I use dynamic SQL whenever needed vs avoiding it. I'll take nanoseconds of
run time vs logical complexity for embedded SQL.

When creating applications where the user input is used to create the SQL,
dynamic SQL makes much more sense in cases where there are multiple
selections, sorting options, etc.

Unless the options you present your users are simple enough to allow
embedded SQL. Or you're using the SQL to verify data (ie, is a customer
active... is an item number valid... etc).

But when you have a web/green screen that allows sorting and selecting
using multiple criteria and sorting options, you'll be hard pressed to do
that without dynamic SQL statments.

Case in point.. go here:
http://www.bvstools.com:5250/cgi-bin/cstlst

Selected "Detailed Search". Now, show me the code to do something like
that without dynamic SQL.

There are cases for both, and the use for them should be obvious. I would
think trying to use a host variable to house a variable CASE would be one
of the perfect cases for dynamic SQL.

Brad
www,bvstools.com

On Wed, Feb 25, 2015 at 7:36 AM, Gary Thompson <gthompson@xxxxxxxxxxx>
wrote:

Birgitta,

Thank you for your detailed explanation.
To check my understanding of dynamic SQL; is it true that changing the
library of all tables is one case where an SQL PREPARE is appropriate ?

-----Original Message-----
From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of
Birgitta Hauser
Sent: Tuesday, February 24, 2015 11:12 PM
To: 'RPG programming on the IBM i (AS/400 and iSeries)'
Subject: AW: Using host variable in embedded sql

I second the use of dynamic SQL...

I avoid dynamic SQL whenever possible.
... and in around 95% of all cases the request can be done with static SQL.
The only situation where dynamic SQL is really needed is, if the tables,
views or schemas cannot be determined before runtime.

Even though we talk about nanoseconds, dynamic SQL requires more work at
runtime (Syntax Check, building the access path).
And if you won't work with parameter markers, i.e. prepare once and
execute multiple times, each time the prepare statement is run a FULL OPEN
(which includes the most time consuming part of the query execution,
opening the data path) must be performed. That means the cursor is not
reusable.

When using static SQL the chance that the ODP (Open Data Path) is reused
is much higher, at least if you do not use compile Option/Set Option
CLOSQLCSR=*ENDMOD and do not run your SQL Statement in a program compiled
with activation group *NEW.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser

"Shoot for the moon, even if you miss, you'll land among the stars." (Les
Brown)
"If you think education is expensive, try ignorance." (Derek Bok) "What is
worse than training your staff and losing them? Not training them and
keeping them!"

-----Ursprüngliche Nachricht-----
Von: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] Im Auftrag von
Bradley Stone
Gesendet: Tuesday, 24.2 2015 23:50
An: RPG programming on the IBM i (AS/400 and iSeries)
Betreff: Re: Using host variable in embedded sql

I second the use of dynamic SQL...

I use them all the time when the selection, sorting and/or anything else
isn't obvious and driven by user input.

Brad
www.bvstools.com

On Tue, Feb 24, 2015 at 4:36 PM, D*B <dieter.bender@xxxxxxxxxxxx> wrote:

... SQL is a striongly typed language => you can't put a fieldname
into a host variable, or into a parameter marker!!!
What would work is, to prepare a dynamic assembled string - with the

risc.

that it would blow up at preparetime - but mostly there are better
alternatives.

D*B
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