Re: Embedded SQL and Parameter Markers

Hi Birgitta,

this is what I thought also - even if some „SQL-gurus“ think, that this kind of WHERE clause is a no-no.

Do you have any idea for doing the same with sorting?

We do dynamic (user-selectable) sorts, and it would be great to use static SQL instead of dynamic. But for sorting, I found no static solution so far.

Kind regards,
Daniel

Am 17.02.2022 um 15:08 schrieb Birgitta Hauser <Hauser@xxxxxxxxxxxxxxx>:

I'd use static SQL:

Declare Cursor ...
Select ...
From ...
Where Field1 = Case When :Filter1 <> '' Then :Filter1 else Field1
And Field2 = Case When :Filter2 <> 0 Then :Filter2 Else Field2
And Field3 = Case When :Fillter3 > '2000-01-01' Then :Filter3
else Field3
... and so on

If no value is entered in the filter, Field = Field is performed, i.e.
everything is returned.

Mit freundlichen Grüßen / Best regards

Birgitta Hauser


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-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Craig
Richards
Sent: Donnerstag, 17. Februar 2022 10:15
To: RPG programming on the IBM i (AS/400 and iSeries)
<rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Embedded SQL and Parameter Markers

I'm building a few "Work With" screens with filters at the moment Fairly
typical maintenance programs where several of the columns shown in a subfile
have a "filter" field above them for refining the record selection.

Because the number of filters used is variable, I have traditionally created
dynamic SQL by building up a WHERE clause in a string and adding in any of
the filter fields which have been entered on the screen by the user.

I was wondering if there is a reasonable way to do this using parameter
markers.
Given that the number of filters entered is variable, so would the list of
parameter markers be.

To illustrate - I'm doing something like (simplified for brevity):

SqlStm = 'Select ... From ...';

If Filter1 <> *Blanks;
SqlWhere += 'and Field1 = Filter1'
EndIf;

If Filter2 <> *Blanks;
SqlWhere += 'and Field2 = Filter2'
EndIf;

If SqlWhere <> *Blanks;
SqlStm += SqlWhere;
EndIf;

etc.

In this simple example I could end up with:
- Select * from File
- Select *from File where Field1 = Value1
- Select *from File where Field2 = Value2
- Select *from File where Field1 = Value1 and Field2 = Value2

Is there a better way to build this dynamic sql?

Thanks in advance for any suggestions.
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