多条件情况查询，sql select case when when else

多条件情况查询

SELECT
     Title,
    'Price Range' =
    CASE
        WHEN price IS NULL THEN 'Unpriced'
        WHEN price < 10 THEN 'Bargain'
        WHEN price BETWEEN 10 and 20 THEN 'Average'
        ELSE 'Gift to impress relatives'
    END
FROM titles

select *,case when ActualTime is null then null  when PlanTime  is null then null  else   ISNULL(ActualTime, 0) - ISNULL(PlanTime, 0)   end    as   Difference
         from KPI_TaskActivities