create cummulative total in query

julian_morgan

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Hi All, hope you can help.

I have an access 2007 query with the following fields:

Despatch_Date (many records)
Order_Number (many records per despatch_date)
Line_Number (many records per Order_Number)
Production_Time (varies with each Order_Number and Line_Number combination)

The Goal is to make a unique record identifier out of these fields and then use it to allow me to use Dsum or similar to make a running total of the Production_Time field (as you would expect Despatch_Date will have duplicates in it). All i want is to show a production completion time for each record by perhaps adding, for each record, the cumulative total of field Production_Time to "now()".

I have tried various expression fields in my query to get a unique ID for each row from concatenating or adding fields, and that seems to give me a unique number. but running Dsum or dcount just gives me an error or zero even when i force the unique value to be a double or integer.

Help much appreciated anyone?
 

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