Question

我有一个表（myItems），其中有一个＆＃34; id＆＃34;和＆＃34; date＆＃34;。现在我想宣读一下，每月有多少项目（我也想区分2013年10月到2014年10月）。

我开始时：

SELECT Count(okt.id) AS Oktober, Count(nov.id) AS November
FROM    `myItems` as okt,
        `myItems` as nov    
WHERE (okt.date between '2013-10-01' and '2013-10-31') 
   OR (nov.date between '2013-11-01' and '2013-11-30')

但它打印出一个非常大的数字。我做错了什么？

Answer 1

试试这个。这会将数据分成几个月，然后执行COUNT：

SELECT SUM(CASE WHEN MONTH(date) = 10 THEN 1 ELSE 0 END) AS Oktober
     , SUM(CASE WHEN MONTH(date) = 11 THEN 1 ELSE 0 END) AS November
FROM    `myItems`

演示：SQL Fiddle

YEAR整合：

SELECT 2013 as Year
     , SUM(CASE WHEN MONTH(date) = 10 THEN 1 ELSE 0 END) AS Oktober
     , SUM(CASE WHEN MONTH(date) = 11 THEN 1 ELSE 0 END) AS November
FROM    `myItems`
WHERE YEAR(date) = 2013
UNION ALL
SELECT 2014 as Year
     , SUM(CASE WHEN MONTH(date) = 10 THEN 1 ELSE 0 END) AS Oktober
     , SUM(CASE WHEN MONTH(date) = 11 THEN 1 ELSE 0 END) AS November
FROM    `myItems`
WHERE YEAR(date) = 2014;
;

演示：Fiddle

灵感来自@ user77318

SELECT YEAR(date) as Year, month(date) as month, count(id) as count 
FROM myItems 
GROUP BY YEAR(date), MONTH(date);

我个人推荐这个，更漂亮。然后，您可以在应用层上完成所有演示文稿。

Answer 2

试试这个。按月对结果进行分组：

选择月份（日期）作为月份，计数（id）作为计数FROM myItems日期之间的日期＆＃39; 2013-10-01＆＃39;和＆＃39; 2013-11-30＆＃39;按月分组（日期）;

输出结果示例：

月|计数

10 | 100

11 | 200

Answer 3

可能你没有使用加入，你只是给出条件。首先尝试将这两个表与主键或一些唯一且通用的数据列连接起来。然后尝试执行上面的查询。 Somthiong是这样的： -

SELECT Count(okt.id) AS Oktober, Count(nov.id) AS November
FROM    `myItems` as okt,
        `myItems` as nov    
WHERE okt.id = nov.id
AND (okt.date between '2013-10-01' and '2013-10-31')
OR (nov.date between '2013-11-01' and '2013-11-30');

这可能对你有帮助。

如何根据时间（月，年）计算记录？

3 个答案: