Re: SQL with parameters - need to PREPARE and 'OPEN ... USING'?

Hi Paul

Sql Static means the structure of your sql do not change in your program
and it is hardcoded.
.
Usually you use Dynamic sql when you need to build the sql statement in a
string, when the sql statement is built on the fly.
dynamic SQL refers to SQL commands that are interpreted at runtime, your
program doesn't know ahead of time how your sql
going to be, it needs to be built into a variable then execute this
variable as an SQL statement, the sql statement is dynamic
in nature and can be changed at runtime based on input parameters, it
require more resource at run time since it needs
to prepare the statement, interpreted and then executed.

let's say for example you have this situation
Select;
When UpdByDept;
Stmt = SelectStmt + 'Dept = ?' + ForUpdate;
CompareValue = DeptID;
When UpdByJob;
Stmt = SelectStmt + 'Job = ?' + ForUpdate;
CompareValue = Pos;
When UpdByDate;
Stmt = SelectStmt + 'HireDate < ?' + ForUpdate;
CompareValue = StartDate;
EndSl;

As you can see the select statement is built based on different criteria
which change the structure of your sql in your program,
this particular example is using parameters marker that's when you need to
use the sintax "USING: parm1 :parm2 :parm3 etc. etc.

with a dynamic sql you must use Prepare and you could use Execute or
Execute Immediate.




On Wed, May 11, 2016 at 1:56 PM, <dlclark@xxxxxxxxxxxxxxxx> wrote:

"RPG400-L" <rpg400-l-bounces@xxxxxxxxxxxx> wrote on 05/11/2016 01:39:55
PM:

I assume you had a PMR open? The answer they came back with was to use
dynamic SQL?

There was no PMR. We were having performance issues and we hired
IBM to, among other things, take a look at our SQL usage and to advise us
the correct/best way to use SQL. One of the things that came out in the
process was that our environment has nearly 600 "local" data libraries
with the same tables in every library plus we have a "shared" data
library. Library lists will have one "local" data library and the one
"shared" data library in them. "Local" users don't switch library lists
for their interactive sessions but some of the jobs that run on their
behalf have to switch library lists to process all of the files. The
resulting IBM recommendation to us was to use static SQL for the "shared"
data library but to use dynamic SQL for the "local" data libraries. We
also contracted for SQL training and the trainer agreed regarding our
situation with the same table names in multiple data libraries.

Sincerely,

Dave Clark
int.ext: 91078
direct: (937) 531-6378
home: (937) 751-3300

Winsupply Group Services
3110 Kettering Boulevard
Dayton, Ohio 45439 USA
(937) 294-5331





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