SQL 怎么写计算上季度的采购金额啊

[sx_zyb]

我表的格式是：
年 季度 本季度采购总金额 本季度成都采购金额 上季度采购总金额 上季度成都采购金额
这个是我要的格式

select YEAR (c.入库时间) 年,
cast (DATEPART (QUARTER,c.入库时间) AS VARCHAR (2))+'季度' as 季度,
SUM (c.采购金额) AS 本季度药品采购总金额,
SUM (c.四川造金额) AS 本季度四川造采购金额,
sum(
case cast (DATEPART (QUARTER,c.入库时间) AS VARCHAR (2))
when cast (DATEPART (QUARTER,c.入库时间)-1 AS varchar(2))
then c.采购金额
else 0
end ) AS 上季度药品采购总金额,
sum(
case cast (DATEPART (QUARTER,c.入库时间) AS VARCHAR (2))
when cast (DATEPART (QUARTER,c.入库时间)-1 AS varchar(2))
then c.四川造金额
else 0
end ) AS 上季度川造采购金额
from dbo.FACT_采购明细 C
group by YEAR(c.入库时间),(cast(datepart(q,C.入库时间) as varchar(2))+'季度')
order by YEAR (c.入库时间), cast (DATEPART (QUARTER,c.入库时间) AS VARCHAR (2))+'季度'

这个是我写的。但是查询结果不对，我暂时要找不出愿意，求救大家啊 。。。