How to retrieve the data from db in progress 4gl? - openedge

Question

How to fetch the value from db in progress 4gl, initially have a input from user to select the record based on the value the record will be displayed. we try that but we can't fetch the exact value.
This is our program:
def var b as int.
def var obj as int.
/*set obj.
prompt-for obj.*/
def var sum as int.
def var a as int no-undo.
def var i as int no-undo.
for each po_mstr break by po_nbr.
select count (*) from po_mstr.
assign
a = 1
b = 583 .
repeat:
if first-of (po_nbr) then
set obj.
prompt-for obj.
if (a le obj and obj lt b) then
disp po_nbr po_vend po_ship po_ord_date with 2 col.
end.
end.
I can retrieve a single data only if we give more than 2 value means it will display the same first value.

Answer 1

Let's break this down. You're using a lot of commands without really realizing what they're for.
FOR EACH opens a block and perform record reads for each loop, in the selected sorting order (if none is selected, then it uses the primary index).
SELECT will perform a database operation, not necessarily doing on the fly, but it might.
REPEAT will also open a block, in which you might or might not be looping records with additional commands. Having said that, here's how I'd write this:
def var a as int no-undo.
def var b as int.
def var sum as int.
/*
def var obj as int.
update obj.
def var i as int no-undo.
you're not using this */
select count (*) into sum from po_mstr.
/* is this what you wanted? To have the count in sum? I don't see a reason, but suit yourself */
assign a = 1 b = 583 . /* or use UPDATE a b. if you would like to make that variable */
/* Since a and b are not changing, I moved it to outside the loop */
for each po_mstr where po_nbr >= a and po_nbr < b:
disp po_nbr po_vend po_ship po_ord_date with 2 col.
end.
I took some liberties. I removed obj because as far as I could assess, you were trying to copy po_nbr values to it, then use it to see if it was in the range you wanted to see. Since I believe po_nbr stands for po number, and that is probably unique, I'd also guess every iteration will have a different value for it. So no need to use if first-of. It also eliminates the need to copy it to a variable. Just compare it directly to the range of po's you want to see. Finally, the display should be fine.
I'm going to go ahead and assume your team hasn't been trained. This would be very important going forward, because QAD (any ERP software, in fact) is going to inflate really fast and badly written code, even when harmless, may impact performance and usability, which could be a problem to operation as a whole. Stack Overflow may be helpful for punctual questions, but the kind of problems you will run into if you aren't prepared will likely not be possible to solve here.
Hope this helps.