quote:

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Originally posted by Bustaz Kool

Instead of using OrderDate, use DateAdd(Month, DateDiff(Month, 0, OrderDate), 0). This does assume that OrderDate is a datetime.

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--   If you don't want to group by Cliente,
--   remove it from the select list and the group by list.  
SELECT pa.nome      AS Cliente,
       DATEADD(mm, DATEDIFF(mm, 0, pa.pdata), 0) AS [FirstOfMonth],
       AVG(mh.moh)  AS 'Média Horas Serviço 3M',
       AVG(mh.deh)  AS 'Média Kms Deslocação 3M'
FROM   pa
       JOIN sn
            ON  pa.snno = sn.snno
       JOIN mh
            ON  mh.nopat = pa.nopat
WHERE  sn.snno <> 0
       AND pa.pdata >= DATEADD(mm, DATEDIFF(mm, 0, GETDATE()) -4, 0)
       AND pa.pdata < DATEADD(mm, DATEDIFF(mm, 0, GETDATE()), 0)
GROUP BY
       pa.nome,
       DATEADD(mm, DATEDIFF(mm, 0, pa.pdata), 0)