用SQL Server HAVING子句计算列和平均值

DECLARE @Avg money
SELECT @Avg = dbo.AverageSale_fns()
SELECT 
      *, @Avg as Average,
      TotalSale / @Avg as Ratio,
      CASE 
            WHEN TotalSale / @Avg > 1 THEN 'Above Average'
            WHEN TotalSale / @Avg < 1 THEN 'Below Average'
            ELSE 'Average'
      END

FROM dbo.SalesTotals_fnt()