calculating difference between the same field of different records

[jgravlin01]

I'm very new to Access and don't exactly know what I'm doing. I have a database that measures the meter readings on different machines. Each machine has its own table. There's a new record for each day. The two fields I'm working with right now are the ID and one called EndOfDayReading, which as you can tell is the number on the meter at the end of each day. I need to show on my report the value of each day's reading minus the day before's.

I'm pretty sure you do this with a query but I have no clue how. Some Google searching led me to believe you need to know either SQL or VBA to do this, but my boss insists there's an easy way, although he doesn't know what it is. I could do this easily with a spreadsheet but he insists on a database.

Using Access 2007 by the way.

 

[Uncle Gizmo]

I think what you want is " running sum" or a "running balance", there are some good examples on "Roger's access library" try this one here: http://www.rogersaccesslibrary.com/forum/topic279.html

 

[Alansidman]

Here is a tutorial

http://www.techonthenet.com/access/queries/weight.php

and here is a solution I like

http://support.microsoft.com/default.aspx?scid=kb;en-us;210504

Alan