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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