Suppressing the prefix on a concatenated expression when the underlying control is null, or empty.

I have a control on a form for which the data source is an autonumber field in a table. This number is used as a purchase order number in my database, however my PO numbers are all prefixed with the letters "CC". The control pointing to the data field is hidden in my form, and I have an unbound control which contains the expression ="CC" & [PONumber] so that the number will display on my form as CC12345 for instance.

I have many records for which a PO number has not been assigned yet, and they all display the "CC" with no trailing PO number. Is there a way for me to suppress the "CC" in my expression so that it will only display in the records which actually have PO numbers in them?
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Dany BalianConnect With a Mentor CTOCommented:
Or if i misunderstood u in my previous post:
Select iif(isnull(ponumber),'','CC' & ponumber) ....
Dany BalianCTOCommented:
Have you tried mid(ponumber,3,100)??
Dale FyeCommented:
Assuming the [poNumber] is NULL, you can use the + operator rather than the & to concatenate the data.

ControlSource: = "CC" + [poNumber]
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Dale FyeCommented:
Just so you understand, when the ampersand (&) is used to concatenate two items, and one of them is NULL, the result is the non-null value:

"A" & NULL = "A"

But when you use the plus sign as the operator, then if either side of the equation is NULL, then the result will be NULL


Although technically, you cannot "= NULL"
Dale FyeCommented:
glad I could help.
Dale FyeCommented:
ref you personal message:

" I have many records for which a PO number has not been assigned yet,"

I don't understand how this can be an autonumber field as described in your initial statement above and still have PO numbers not yet assigned.  Can you please confirm the data type of PONumber?
Shooter54Author Commented:
The data type of the PONumber field in the underlying table is autonumber. This number is created when I select a range of line items and run a query which creates a new record in my PO table, then the PONumber control in my form is updated to include the new PONumber which was just generated. Does that help?
Dale FyeCommented:
Actually, since this is numeric and not a string, Dany's solution is probably the best option:

ControlSource:= iif(isnull(ponumber),'','CC' & ponumber)

you should probably click the Request Assistance hyperlink at the bottom right of your original post and ask the moderator to reopen the question so you can reassign points.

So, you have something like an orders table and a PO table.
This form is based on a query that joins them both.
An order can exist that does not yet have a PO Number
There is an excellent Article about the nice trick @Dale has suggested here

Access can do some fun things with null and the concatenator operators + and &.  Read about it.  @harfang explains it better than I ever could.

Now your expression is currently
="CC" & [PONumber]

But you don't want the CC if PONumber is null
So try
if PONumber is null then  nothing,
else, CC and the PO number

That should do it too
Shooter54Author Commented:
=IIF(isnull([PONumber]),"","CC"&[PONumber]) was the solution I was looking for. Thank you for all your help. I have requested assistance so the points can be reassigned.
Dany BalianCTOCommented:
@dale Thanks for ur suggestion!
@shooter glad i could help.. Good luck on ur project
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