Assistance with Query Calculation - Previous Month Total

[AseretinMO]

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I am new to queries and need to create a calculation that will return the Net Gain/Loss for the Prior Month


SELECT [Mock Data].[Curent Month_Date], [Mock Data].[Agent ID], [Mock Data].[Customer ID], [Mock Data].[Customer Name], [Mock Data].[Beginning Balance], [Mock Data].[Monthly Payment], [Mock Data].[Net Gain/Loss], [Mock Data].[Ending Balance], [Curent Month_Date]-1 AS [Prior Month]
FROM [Mock Data];

[ranman256]

in a form, youd have 2 text boxes with txtSTartDate and txtEndDate,
the query , qsCurrentMonth, would pull the data from these dates.

i have an extra 2 text boxes, txtPrevStartDate and txtPrevEndDate
(i make them automatic: txtPrevStartDate = DateAdd("m",-1,txtSTartDate)
the query , qsPrevMonth, would pull the data from these dates.

the final query pulls data from both to show them together

[pbaldy]

Another thought:

http://allenbrowne.com/subquery-01.html#AnotherRecord