I've got this table:

CREATE TABLE #Data1 
    (
    [Market] VARCHAR(100) NOT NULL, 
    [Operator] VARCHAR(100) NOT NULL,                                                                   
    [Date] DATETIME NOT NULL,   
    [Measure] VARCHAR(100) NOT NULL, 
    [Amount] NUMERIC(36,10)  NOT NULL, 
                --new calculated fields 
    [DailyAvg_30days] NUMERIC(38,6) NULL    DEFAULT 0                                   
    )

I've populated all the fields apart from DailyAvg_30days.
This field needs to show the total for the preceding 30 days e.g.
1. if Date for a particular record is 2nd Dec then it will be the total for the period 3rd Nov - 2nd Dec inclusive.
2. if Date for a particular record is 1st Dec then it will be the total for the period 2nd Nov - 1st Dec inclusive.

My attempt to try to find these totals before updating the table is as follows:

SELECT 
    a.[Market],
    a.[Operator],
    a.[Date],
    a.[Measure],
    a.[Amount],
    [DailyAvg_30days] = SUM(b.[Amount])
FROM 
    #Data1 a
    INNER JOIN #Data1 b
        ON 
        a.[Market] = b.[Market] AND
        a.[Operator] = b.[Operator] AND
        a.[Measure] = b.[Measure]   AND
        a.[Date] >= b.[Date]-30 AND
        a.[Date] <= b.[Date]
GROUP BY
    a.[Market],
    a.[Operator],
    a.[Date],
    a.[Measure],
    a.[Amount]
ORDER BY 1,2,4,3

Is this a valid approach or do I need to approach this from a different angle?