如何将两个SQL查询组合成一个查询

我有一张如下图所示的桌子： 问题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年-月-日

问题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年-月-日

我想用一个查询显示两个结果。

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请帮帮我！谢谢大家

只需将这两个选项都放在select上，如下所示：

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)

---

只需将这两个选项都放在select上，如下所示：

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)

---

如果需要在一行中同时显示两个结果：

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)
)

如果需要不同行中的结果，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)
)

---

如果需要在一行中同时显示两个结果：

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)
)

如果需要不同行中的结果，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)
)

---

对于您的特定情况，您可以使用交叉连接来获得结果

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;

---

对于您的特定情况，您可以使用交叉连接来获得结果

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;

---

选择最大值、最小值…？返回空值。where子句是difference，我得到的结果是2个差异记录的2个结果：您需要两个结果在一行中还是在不同的行中？我希望两个结果在一行中。选择max，min…？返回NULL。2 where子句是差异，而我得到的2个结果是2个差异记录的2个结果：您需要两个结果在一行中还是在不同的行中？我希望两个结果都在一行中。我的“where”子句是差异my“where”子句是差异case expression查询是最好的方法！case表达式查询就是最好的选择！非常感谢。这很容易非常感谢。这很容易