SQL Server：订单日期和之前的订单答案

【问题标题】：SQL Server : order date and orders beforeSQL Server：订单日期和之前的订单
【发布时间】：2017-03-27 03:58:38
【问题描述】：

我有一个简单的Customers (customerID) 表和一个Orders (orderID, orderdate) 表

我需要获取正好两周前下订单的所有客户的列表，以及他们在那周之前收到的所有订单的数量。

SELECT c.id_customer
FROM customer AS c
JOIN order AS o ON o.customerID = c.customerID
WHERE o.delivery_date = DATEADD(Day,-14,GETDATE())

但我直到那周才知道如何计算订单数。

【问题讨论】：

标签： sql-server tsql

【解决方案1】：

您可以使用<= 获取行并使用having 子句检查在给定日期是否存在行：

select c.id_customer, count(*) as order_count
from customer as c
join orders as o on o.customerID = c.customerID
where o.delivery_date <= DATEADD(Day, - 14, GETDATE())
group by c.id_customer
having count(case when o.delivery_date = DATEADD(Day, -14, GETDATE()) then 1 end) > 0;

另请注意，我将表名 order 更改为 orders，因为 order 是 SQL 保留关键字，使用关键字作为表/列标识符通常是个坏主意。

【讨论】：

【解决方案2】：

SELECT c.customerID,o.orderID, count(o.delivery_date)
FROM customer AS c
JOIN order AS o ON o.customerID = c.customerID
WHERE o.delivery_date = DATEADD(Day,-14,GETDATE())
group by c.customerID,o.orderID

【讨论】：

【解决方案3】：

用其他样本数据试试这个，

 Declare @DaysAgo int=14 --para to be pass in proc
    declare @To Datetime=DATEADD(second,-1,cast((DATEADD(Day, - (@DaysAgo-1), cast(GETDATE() as date)) ) as DATETIME))
   declare @From Datetime=cast((DATEADD(Day, - @DaysAgo, cast(GETDATE() as date)) ) as DATETIME)


    select c.id_customer, count(*) as order_count
    from customer as c
    join orders as o on o.customerID = c.customerID
    where o.delivery_date >= @From AND 
    o.delivery_date <= @To
    group by c.id_customer

【讨论】：