每月获取记录，但如果当月没有记录，则为零答案

【问题标题】：Get Record Per Month But Also Get Zero If No Records That Month每月获取记录，但如果当月没有记录，则为零
【发布时间】：2017-01-19 14:30:22
【问题描述】：

如果我有以下 SQL 表

测试

id   type   receiveDate
 1   Blood   2012-01-18
 2   Blood   2012-01-20
 3   Blood   2012-01-18
 4   Blood   2012-03-01
 5   Blood   2012-05-21
 6   Blood   2012-05-18
 7   Blood   2012-06-14
 8   Blood   2012-07-22
 9   Blood   2012-07-29
 10  Blood   2012-12-04
 11  Blood   2012-12-30

然后我运行查询

SELECT COUNT(*)
FROM Tests 
WHERE YEAR(receiveDate) = '2012' 
GROUP BY MONTH(receiveDate)

我会回来的

COUNT(*)
 3
 1
 2
 1
 2
 2

我的问题是，即使那个月没有记录，有没有办法找回所有十二个月？所以例如我想得到

的输出

另外，作为额外的奖励，有没有办法用计数来显示月份？谢谢！

【问题讨论】：

做过研究吗？像google.com/… 或类似的东西？
额外奖励？我原以为这是一个基本要求:-(

标签： mysql

【解决方案1】：

SELECT  Months.m AS month, COUNT(Tests.receiveDate) AS total FROM 
(
    SELECT 1 as m 
    UNION SELECT 2 as m 
    UNION SELECT 3 as m 
    UNION SELECT 4 as m 
    UNION SELECT 5 as m 
    UNION SELECT 6 as m 
    UNION SELECT 7 as m 
    UNION SELECT 8 as m 
    UNION SELECT 9 as m 
    UNION SELECT 10 as m 
    UNION SELECT 11 as m 
    UNION SELECT 12 as m
) as Months
LEFT JOIN Tests  on Months.m = MONTH(Tests.receiveDate)  
GROUP BY
    Months.m

如果你想要特定年份，那么试试这个。

SELECT  Months.m AS month, COUNT(Tests.receiveDate) AS total FROM 
(
    SELECT 1 as m 
    UNION SELECT 2 as m 
    UNION SELECT 3 as m 
    UNION SELECT 4 as m 
    UNION SELECT 5 as m 
    UNION SELECT 6 as m 
    UNION SELECT 7 as m 
    UNION SELECT 8 as m 
    UNION SELECT 9 as m 
    UNION SELECT 10 as m 
    UNION SELECT 11 as m 
    UNION SELECT 12 as m
) as Months
LEFT JOIN Tests on Months.m = MONTH(Tests.receiveDate)  
AND YEAR(Tests.receiveDate) = '2012'
GROUP BY Months.m

【讨论】：

【解决方案2】：

这是一种替代方法，可连续显示当年的所有结果。

SELECT 
    SUM(if(MONTH(receiveDate) = 1, 1,0)) as Jan,
    SUM(if(MONTH(receiveDate) = 2, 1,0)) as Feb,
    SUM(if(MONTH(receiveDate) = 3, 1,0)) as Mar,
    SUM(if(MONTH(receiveDate) = 4, 1,0)) as Apr,
    SUM(if(MONTH(receiveDate) = 5, 1,0)) as May,
    SUM(if(MONTH(receiveDate) = 6, 1,0)) as Jun,
    SUM(if(MONTH(receiveDate) = 7, 1,0)) as Jul,
    SUM(if(MONTH(receiveDate) = 8, 1,0)) as Aug,
    SUM(if(MONTH(receiveDate) = 9, 1,0)) as Sep,
    SUM(if(MONTH(receiveDate) = 10, 1,0)) as Oct,
    SUM(if(MONTH(receiveDate) = 11, 1,0)) as Nov,
    SUM(if(MONTH(receiveDate) = 12, 1,0)) as `Dec`
FROM test 
WHERE YEAR(receiveDate) = '2012' 
  AND type = 'Blood'

结果是

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
3   0   1   0   2   1   2   0   0   0   0   2

如果您想在一年中报告不止一种类型

SELECT type,
    SUM(if(MONTH(receiveDate) = 1, 1,0)) as Jan,
    SUM(if(MONTH(receiveDate) = 2, 1,0)) as Feb,
    SUM(if(MONTH(receiveDate) = 3, 1,0)) as Mar,
    SUM(if(MONTH(receiveDate) = 4, 1,0)) as Apr,
    SUM(if(MONTH(receiveDate) = 5, 1,0)) as May,
    SUM(if(MONTH(receiveDate) = 6, 1,0)) as Jun,
    SUM(if(MONTH(receiveDate) = 7, 1,0)) as Jul,
    SUM(if(MONTH(receiveDate) = 8, 1,0)) as Aug,
    SUM(if(MONTH(receiveDate) = 9, 1,0)) as Sep,
    SUM(if(MONTH(receiveDate) = 10, 1,0)) as Oct,
    SUM(if(MONTH(receiveDate) = 11, 1,0)) as Nov,
    SUM(if(MONTH(receiveDate) = 12, 1,0)) as `Dec`
FROM test 
WHERE YEAR(receiveDate) = '2012'
GROUP by type;

结果是：

type    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Blood   3   0   1   0   2   1   2   0   0   0   0   2
Sweat   2   1   0   0   1   0   0   0   0   0   0   0
Tears   0   0   1   2   0   0   0   0   0   0   0   0

【讨论】：