select-case

declare  @fff varchar(50)
declare  @ddd int

select @ddd = 20
SELECT    @fff =
      CASE
         WHEN @ddd < 10 THEN '小于10'
         WHEN @ddd > 10 and @ddd < 20 THEN '10到20之间'
  WHEN @ddd > 20 and @ddd < 30 THEN '20到30之间'
  WHEN @ddd > 30 and @ddd < 40 THEN '30到40之间'
  WHEN @ddd > 40 and @ddd < 50 THEN '30到40之间'
         ELSE '10，20，30，40，50'
      END

select @fff