对于SQL Server，我很难理解时间之间的差异
我正在使用SQuirell客户端，但不确定Datediff是否为函数
我的数据示例
Person | Times Ordered | Date order placed | Date order placed (Timestamp)
---------------------------------------------------------------------
Jane | 1 | 5/5/2017 | 5/5/2017 01:01:56.95
Jane | 2 | 6/2/2017 | 6/2/2017 18:41:34.486
Jane | 3 | 7/5/2018 | 7/5/2018 08:31:45.759
Donald | 1 | 5/2/2017 | 5/2/2017 21:22:44.23
Donald | 2 | 8/2/2018 | 8/2/2018 22:25:50.323
Ron | 1 | 4/8/2017 | 4/8/2017 03:10:25.55
Ron | 2 | 8/30/2017 | 8/30/2017 19:20:20.55
Ron | 3 | 5/24/2018 | 5/24/2018 09:35:55.85
Jim | 1 | 2/15/2017 | 2/15/2017 20:15:55.45
Jim | 2 | 9/6/2018 | 9/6/2018 23:20:50.4
我尝试了以下SQL Server查询
select
a.Person,
a.times_ordered,
a.date_order_placed,
datediff(month, lag(a.Date_order_placed_ts) over(partition by a.persion order by a.date_order_placed)) as Month_Difference
from table_1 a
我遇到的错误
SQLERRMC：MONTH SQL状态：42703 错误代码：-206
SQLERRMC：MONTH SQL状态：56098 错误代码：-727
我正在尝试弄清最近的订单与之前的订单之间的时间差。
所需的输出示例
Person | Times Ordered | Date order placed | Date order placed (Timestamp) | Month_difference
----------------------------------------------------------------------------------------------
Jane | 1 | 5/5/2017 | 5/5/2017 01:01:56.95 | <Null>
Jane | 2 | 6/2/2017 | 6/2/2017 18:41:34.486 | 1
Jane | 3 | 7/5/2018 | 7/5/2018 08:31:45.759 | 13
Donald | 1 | 5/2/2017 | 5/2/2017 21:22:44.23 | <Null>
Donald | 2 | 8/2/2018 | 8/2/2018 22:25:50.323 | 15
Ron | 1 | 4/8/2017 | 4/8/2017 03:10:25.55 | <Null>
Ron | 2 | 8/30/2017 | 8/30/2017 19:20:20.55 | 4
Ron | 3 | 5/24/2018 | 5/24/2018 09:35:55.85 | 9
Jim | 1 | 2/15/2017 | 2/15/2017 20:15:55.45 | <Null>
Jim | 2 | 9/6/2018 | 9/6/2018 23:20:50.4 | 19