如何将 2 SQL 个查询合并为一个

Question

我有一个 table 如下图所示：查询 1：

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

Result: 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)

Result: 2017-01-02 (yyyy-MM-dd)

我想通过 1 个查询显示 2 个结果。请帮我！谢谢大家！

Answer 1

像这样把两者都放在 select 上：

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

如果您需要将两个结果放在一行中：

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)
)

如果您需要不同行的结果，请使用 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

对于您的具体情况，您可以使用 CROSS JOIN 来获得结果

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;

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