SQL:仅将日期与月份和年份列进行比较

Question

我有一张表MonthlyShipments看起来像:

partnumber | quantity | month | year |
part1      |       12 |     6 | 2011 |
part1      |       22 |     5 | 2011 |
part1      |       32 |     4 | 2011 |
part1      |       42 |     3 | 2011 |
part1      |       52 |     2 | 2011 |

我想总结过去3个月的数量,不包括当月.我的where子句目前看起来像:

where
  MonthlyShipments.Month <> MONTH(GETDATE()) AND 
  CAST(
    (CAST(MonthlyShipments.Month as nvarchar(2)) + 
    '-01-' + 
    CAST(MonthlyShipments.Year as nvarchar(4))) as DateTime)
  > DATEADD(m, -4, GETDATE())

它有效,但它的丑陋和侮辱.有什么建议使它更漂亮？非常感谢!

Answer 1

好多了......

DATEDIFF(
    month,
    DATEADD(Year, MonthlyShipments.Year-1900,
        DATEADD(Month, MonthlyShipments.Month-1, 0)
           ),
    GETDATE()
    ) BETWEEN 1 AND 3

但是嵌套的DATEADD可以成为计算和索引的列

ALTER TABLE MonthlyShipments ADD
    ShipDate AS DATEADD(Year, MonthlyShipments.Year-1900,
            DATEADD(Month, MonthlyShipments.Month-1, 0)
               )

这使

WHERE DATEDIFF(month, ShipDate, GETDATE()) BETWEEN 1 AND 3