SELECT COALESCE(G.Custid, B.CustID) AS CustID,
       ISNULL(G.Count_Of_PAR, 0),
       ISNULL(B.Count_Of_NPAR, 0)
FROM   (
           SELECT [Custid],
                  ISNULL(COUNT(DISTINCT Custid), 0) AS Count_Of_PAR
           FROM   [DEV].[dbo].[Trans]
           WHERE  complete_date >= '09/30/2012'
                  AND complete_date < DATEADD(DAY, 1, '09/30/2012')
                      AND Category = 'PAR'
           GROUP BY
                  Custid
       ) G
       FULL JOIN (
                SELECT IP.[Custid],
                       ISNULL(COUNT(DISTINCT Custid), 0) AS Count_Of_NPAR
                FROM   [DEV].[dbo].[Trans]
                WHERE  complete_date >= '09/30/2012'
                       AND complete_date < DATEADD(DAY, 1, '09/30/2012')
                           AND Category = 'NPAR'
                GROUP BY
                       IP.[Custid]
            )B
            ON  G.Custid = B.Custid;

SELECT
	CustID,
	COUNT( DISTINCT CASE WHEN category = 'PAR' THEN Custid END) AS Count_Of_PAR,
	COUNT( DISTINCT CASE WHEN category = 'NPAR' THEN Custid END) AS Count_Of_NPAR
FROM
	[DEV].[dbo].[Trans]
WHERE
	complete_date >= '09/30/2012'
	AND complete_date < DATEADD(DAY, 1, '09/30/2012')
GROUP BY
	[Custid];