Try the following snippet. You can call the the below stored procedure from your application, so that NoOfUses in the coupon table will be updated.
CREATE PROCEDURE [dbo].[sp_UpdateCouponCount]
AS
Declare @couponCount int,
@CouponName nvarchar(50),
@couponIdFromQuery int
Declare curP cursor For
select COUNT(*) as totalcount , Name as name,couponuse.couponid as couponid from Coupon as coupon
join CouponUse as couponuse on coupon.id = couponuse.couponid
where couponuse.id=@cuponId
group by couponuse.couponid , coupon.Name
OPEN curP
Fetch Next From curP Into @couponCount, @CouponName,@couponIdFromQuery
While @@Fetch_Status = 0 Begin
print @couponCount
print @CouponName
update Coupon SET NoofUses=@couponCount
where couponuse.id=@couponIdFromQuery
Fetch Next From curP Into @couponCount, @CouponName,@couponIdFromQuery
End -- End of Fetch
Close curP
Deallocate curP
Hope this helps!