如何将2个SQL查询合并为一个

Question

我有一张如下图所示的表格： 查询1：

Select  MIN(SaleStartDate) as MinSaleDate 
from Sales 
where LessonID=1 and (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleStartDate) > 0)

  

    

结果：2017-02-10（yyyy-MM-dd）

  

查询2：

Select  MAX(SaleEndDate) as MaxSaleDate
from Sales 
where LessonID=1 and  (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleEndDate) < 0)

  

    

结果：2017-01-02（yyyy-MM-dd）

  

我想只用1个查询显示2个结果。 请帮我！感谢每一个人！

Answer 1

只需选择这两个：

Select  MIN(SaleStartDate) as MinSaleDate, 
        MAX(SaleEndDate) as MaxSaleDate
    from Sales 
where LessonID=1 and (DATEDIFF(day, 
                               CONVERT (char(10), 
                                        GETDATE(), 
                                        126),
                               Sales.SaleStartDate) > 0)

Answer 2

如果您需要在一行中同时获得两个结果：

Select  
(
Select  MIN(SaleStartDate) as MinSaleDate 
from Sales 
where LessonID=1 
and (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleStartDate) > 0)
),
(
Select  MAX(SaleEndDate) as MaxSaleDate
from Sales 
where LessonID=1 
and  (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleEndDate) < 0)
)

如果您需要在不同行中使用UNION：

Select  
(
Select  MIN(SaleStartDate) as MinSaleDate 
from Sales 
where LessonID=1 
and (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleStartDate) > 0)
) UNION
(
Select  MAX(SaleEndDate) as MaxSaleDate
from Sales 
where LessonID=1 
and  (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleEndDate) < 0)
)

Answer 3

根据您的具体情况，您只需使用CROSS JOIN即可获得结果

SELECT MinSaleDate, MaxSaleDate
FROM
(
    Select  MIN(SaleStartDate) as MinSaleDate 
    from Sales 
    where LessonID = 1 and (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleStartDate) > 0)
),
(
    Select  MAX(SaleEndDate) as MaxSaleDate
    from Sales 
    where LessonID = 1 and  (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleEndDate) < 0)
);

对于一般情况，您可以使用：

SELECT 
    MIN(CASE WHEN (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleStartDate) > 0
            THEN SaleStartDate END) AS MinSaleDate,
    MAX(CASE WHEN (DATEDIFF(day, CONVERT (char(10), GETDATE(), 126), Sales.SaleEndDate) < 0
            THEN SaleEndDate END) AS MaxSaleDate
from Sales 
where LessonID = 1;