Question

如何返回两列各自使用不同WHERE标准的列？显然，这不起作用：

SELECT Name, COUNT(Column1) AS Total, COUNT(Column1) AS YearToDate
FROM Table1
WHERE Occurred_Date BETWEEN '2010-06-01' AND '2010-06-30' --Total
WHERE Occurred_Date BETWEEN '2010-01-01' AND '2010-06-30' --YearToDate

这是我正在寻找的输出：

Name  | Total | YTD  
-------------------
Item1 | 2     | 3
Item2 | 4     | 8

Answer 1

如果为COUNT函数指定列名，则不会计算NULL个值。

因此，简单的方法是使用CASE语句将您不想要的值转换为NULL

SELECT
    Name,
    COUNT(CASE
            WHEN Occurred_Date >= '2010-01-01' AND Occurred_Date < '2011-01-01'
                THEN Occurred_Date
            ELSE NULL
            END) AS [YTD]
    COUNT(CASE
            WHEN Occurred_Date >= '2010-06-01' AND Occurred_Date < '2011-07-01'
                THEN Occurred_Date
            ELSE NULL
            END) AS [MTD]
FROM Table1
GROUP BY Name

我不是100％肯定查询引擎会让你在COUNT中使用CASE（我甚至不确定你正在使用什么数据库平台），但它给你的想法。如果这种方式不起作用，您可以使用派生表编写查询，该表将为您提供相同的结果。

Answer 2

对于UNION来说，这似乎是一个很好的情况。

SELECT Name, COUNT(Column1) AS Total, COUNT(Column1) AS YearToDate
FROM Table1
WHERE Occurred_Date BETWEEN '2010-06-01' AND '2010-06-30' --Total
UNION 
SELECT Name, COUNT(Column1) AS Total, COUNT(Column1) AS YearToDate
FROM Table1
WHERE Occurred_Date BETWEEN '2010-01-01' AND '2010-06-30' --YearToDate

基本上，您分别执行两个查询，然后将它们合并为一组。

不确定您使用的是哪种类型的数据库，但这里是SQL Server和MySql的链接。

Answer 3

您也可以使用

SELECT m.count, ytd.count FROM 
   (SELECT COUNT( id ) count FROM table WHERE date BETWEEN '2010-06-01' AND '2010-06-30') m, 
   (SELECT COUNT( id ) count FROM table WHERE date BETWEEN '2010-01-01' AND '2010-06-30') ytd

Answer 4

你可以在COUNT上使用MySQL IF语句

Answer 5

SELECT COALESCE(CurrMonth.Name, YTD.Name) AS Name, CurrMonth.Total AS Total, YTD.Total AS YearToDate
FROM (
    SELECT Name, COUNT(Column1) AS Total
    FROM Table1 
    WHERE Occurred_Date BETWEEN '2010-06-01' AND '2010-06-30' --Total 
    GROUP BY Name
) AS CurrMonth
FULL OUTER JOIN
(
    SELECT Name, COUNT(Column1) AS Total
    FROM Table1 
    WHERE Occurred_Date BETWEEN '2010-01-01' AND '2010-06-30' --YearToDate 
    GROUP BY Name
) AS YTD
ON CurrMonth.Name = YTD.Name

完整的外连接不是必需的，只是演示了如何处理一个集合不是另一个集合的严格子集的情况。我通常会使用YTD子查询LEFT JOIN到当前月子查询。

另一种策略 - 使用CASE：

SELECT Name
    ,COUNT(CASE WHEN Occurred_Date BETWEEN '2010-06-01' AND '2010-06-30' THEN Column1 ELSE NULL END) AS Total 
    ,COUNT(CASE WHEN Occurred_Date BETWEEN '2010-01-01' AND '2010-06-30' THEN Column1 ELSE NULL END) AS YearToDate
FROM Table1  
WHERE Occurred_Date BETWEEN '2010-06-01' AND '2010-06-30' -- (unnecessary)
    OR Occurred_Date BETWEEN '2010-01-01' AND '2010-06-30'
GROUP BY Name

Answer 6

SELECT Name
    ,SUM(
        CASE WHEN Occurred_Date BETWEEN '2010-06-01' AND '2010-06-30' 
        THEN 1 
        ELSE 0 
        END) AS Total 
    ,SUM(
        CASE WHEN Occurred_Date BETWEEN '2010-01-01' AND '2010-06-30' 
        THEN 1 
        ELSE 0 
        END) AS YearToDate
FROM Table1  
GROUP BY Name

编辑：这应该在SQL Server中有效。

Answer 7

SELECT DISTINCT m.field1, b.field2,

            SUM (CASE
                    WHEN m.created_on >=
                                      TO_DATE ('15/11/2012', 'DD/MM/YYYY')
                    AND m.created_on <
                                   TO_DATE ('15/11/2012', 'DD/MM/YYYY')
                                   + 1
                       THEN 1
                    ELSE 0
                 END
                ) AS count1,
            COUNT (1) AS count2
       FROM table1 m, table2 b
      WHERE m.field1 IN (SELECT DISTINCT field1
                                     FROM table1)
        AND b.field1 = m.field1
   GROUP BY m.field1, b.field2
   ORDER BY count2 DESC;

两列的SQL两个不同的WHERE条件

7 个答案: