ACCESS FEED: Re: [MS_AccessPros] Query to update child totals in parent record

Jumat, 24 April 2015

Re: [MS_AccessPros] Query to update child totals in parent record

Andrew-

Use DCount:

=DCount("POID", "POLines", "POID = " & [POID])

I'm guessing at the key names, but you should get the idea. It might be a little slow, but reasonable - and it'll give you the exact current count every time.

If the list of Purchase Orders doesn't need to be updatable, you can create a query that returns the PO data and the count that will run much faster:

SELECT POHeader.*, LineCount

FROM POHeader INNER JOIN

(SELECT POID, Count(*) As LineCount

FROM POLines

GROUP BY POID) As C

ON POHeader.POID = C.POID

.. and use that as the Record Source of the form.

John Viescas, Author

Microsoft Access 2010 Inside Out

Microsoft Access 2007 Inside Out

Microsoft Access 2003 Inside Out

Building Microsoft Access Applications

SQL Queries for Mere Mortals

http://www.viescas.com/

(Paris, France)

On Apr 24, 2015, at 3:11 PM, Andrew Wilson andrew@adwsystems.co.uk [MS_Access_Professionals] <MS_Access_Professionals@yahoogroups.com> wrote:

Hi John,

Thanks for the response.

I know in theory you should never store calculated fields like this in a table, however the in the real world it's not always possible. J

In the Purchase Order section of this application, the user first sees a list of all the purchase orders in a continuous form, and from there they can select one to edit or delete, or add a new one. The client wanted to see the number of items on each order in this form, so I thought the easiest and fastest, from a form update perspective, way to do it would be to store the count of POLine Items in the POHeader table. Obviously, this can get out of sync, so I need a the query to run occasionally to straighten things out again.

Regards,

Andrew

From: MS_Access_Professionals@yahoogroups.com [mailto:MS_Access_Professionals@yahoogroups.com]
Sent: 24 April 2015 13:19
To: MS_Access_Professionals@yahoogroups.com
Subject: Re: [MS_AccessPros] Query to update child totals in parent record

Andrew-

You should never store a calculated field like this in a table. I assume you're using a form to edit POHeader and a subform to edit POLines. Make the subform a Continuous form and put a text box in the form footer:

=Count(*)

John Viescas, Author

Microsoft Access 2010 Inside Out

Microsoft Access 2007 Inside Out

Microsoft Access 2003 Inside Out

Building Microsoft Access Applications

SQL Queries for Mere Mortals

http://www.viescas.com/

(Paris, France)

On Apr 24, 2015, at 1:58 PM, andrew@adwsystems.co.uk [MS_Access_Professionals] <MS_Access_Professionals@yahoogroups.com> wrote:

Hi All,
Can anyone help with this one.
I have two tables POHeader & POLines, and the POHeader table has a field that keeps track of the number of line items. I need a query that will update the NumLineItems field in the POHeader table with the correct count for the number of Line Items for that POHeader record, if you see what I mean. I can easily do it using VBA, but I'm sure it could be done using a query, but I can't quite get it to work.
Any help greatly appreciated.
Thanks,
Andrew