Question

我试图找出每个订单需要多长时间才能发货。为每个订单提供ordID，客户name和days_to_ship。将它们从最长的延迟（在订单日期和发货日期之间）列出到最短的时间。

SELECT OrdID, name, (ShipDate-orderDate) AS Days_to_Ship
    FROM ORDERS, CUSTOMERS
    WHERE ShipDate-OrderDate=(select Max(ShipDate-OrderDate) from orders)
    ORDER BY Days_to_Ship DESC;

Answer 1

select 
OrdID,name,DATEDIFF(ShipDate,OrderDATE) as Days_to_Ship
from ORDERS, CUSTOMERS    
order by DATEDIFF(ShipDate,OrderDATE) desc;

Answer 2

您尚未指定哪个RDBMS，但您可以在MySql和SqlServer中使用DATEDIFF（略有不同的实现）。 MySql的DateDiff以天为单位返回差异：

select o.OrdID, c.Name, DATEDIFF(o.ShipDate, o.OrderDate) as Days_to_Ship
from ORDERS o 
   INNER JOIN CUSTOMERS c on o.CustomerId = c.CustomerId 
order by Days_to_Ship desc;

对于Sql Server，您需要指定DateDiff的时间间隔，并切换日期：

select o.OrdID, c.Name, DATEDIFF(dd, o.OrderDate, o.ShipDate) as Days_to_Ship
from ORDERS o 
   INNER JOIN CUSTOMERS c on o.CustomerId = c.CustomerId 
order by Days_to_Ship desc;

我假设Customers和Orders之间的加入条件。

如果您只需要最长的延迟，请使用LIMIT 1（MySql）或TOP 1（Sql Server）限制列表 - 与Order By一起使用，您无需评估完全WHERE MAX。

Answer 3

您可以使用DATEDIFF

功能

DATEDIFF(dd, dateTimeField1, dateTimeField2)

其中dd用于区分天数。你也可以使用别人。

像

datepart       Abbreviation
year           yy, yyyy
quarter        qq, q
month          mm, m
dayofyear      dy, y
day            dd, d
week           wk, ww
weekday        dw, w
hour           hh
minute         mi, n
second         ss, s
millisecond    ms
microsecond    mcs
nanosecond     ns

如何在SQL Server中减去两个日期

3 个答案: