select isnull(f.sm,0)+isnull(p.sm,0)-isnull(s.sm,0) sm,isnull(f.id_custom,ISNULL(p.id_custom,s.id_custom)) id_custom,ISNULL(f.dogid,isnull(p.id_dog,s.id_dog)) id_dog from 
	(SELECT sm, ID_CUSTOM, DogID 
		FROM dbo.FinbalContract
		WHERE dat = '20171201'
			and ismark=0
		) AS f 
	full join
	(SELECT SUM(sm) AS sm, id_custom,  id_dog
		FROM dbo.Pay AS p
		WHERE dat >= '20171201'
			and ismark=0
		GROUP BY id_custom, id_dog) as p 
	on p.id_custom=f.ID_CUSTOM and p.id_dog=f.DogID		 
	full join
	(SELECT SUM(sm) AS sm, ID_CUSTOM, id_dog
		FROM dbo.sale
		WHERE dat >= '20171201' 
			AND ismark = 0
		GROUP BY ID_CUSTOM, id_dog) as s
		on p.id_custom=s.ID_CUSTOM and p.id_dog=s.id_dog