如何在sql中根据月份将值的数量分组到列中答案

【问题标题】：How can I group the number of values into columns based on month in sql如何在sql中根据月份将值的数量分组到列中
【发布时间】：2020-06-02 02:20:21
【问题描述】：

我有一个像

这样的数据集

Code Date 
123  21-Jan-2000 
234  23-Feb-1999 
123  19-Jan-2001

我想查询表格以显示如下数据：

Code Total (All months) Jan Feb ... Dec 
123    2                 1   1
234    1                 0   1

我真的不知道如何开始。非常感谢任何提示或帮助。

【问题讨论】：

标签： oracle-sqldeveloper

【解决方案1】：

我们可以尝试透视查询：

SELECT
    Code,
    COUNT(Date) AS "Total (All months)",
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 1  THEN 1 END) AS Jan,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 2  THEN 1 END) AS Feb,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 3  THEN 1 END) AS Mar,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 4  THEN 1 END) AS Apr,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 5  THEN 1 END) AS May,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 6  THEN 1 END) AS Jun,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 7  THEN 1 END) AS Jul,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 8  THEN 1 END) AS Aug,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 9  THEN 1 END) AS Sep,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 10 THEN 1 END) AS Oct,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 11 THEN 1 END) AS Nov,
    COUNT(CASE WHEN EXTRACT(MONTH FROM Date) = 12 THEN 1 END) AS Dec
FROM yourTable
GROUP BY
    Code
ORDER BY
    Code;

请注意，上述显式枢轴语法通常可以胜过使用PIVOT 运算符的对应语法。

【讨论】：

如果所有月份都有 0 个值，是否有办法将总数显示为 0，因为它现在显示为 1
@llamaro25 尝试计算Date 列。仅当给定代码具有一条或多条其Date 为NULL 的记录时，才可能出现总计为零。检查更新的答案。

【解决方案2】：

您想使用PIVOT。来自official documentation：

select * from (
   select times_purchased, state_code
   from customers t
)
pivot 
(
   count(state_code)
   for state_code in ('NY','CT','NJ','FL','MO')
)
order by times_purchased

所以在你的情况下，以下查询：

select * from (
    select code, datepart(month, date) as month
      from #data
) as data
pivot 
(
    count(code)
     for month in ('1','2','3','4','5','6','7','8','9','10','11','12')
)

【讨论】：