如何獲得客戶通過郵寄的天數？

Question

如何獲取客戶已申請了多少天？
圖片告訴我想要得到什麼。我不知道如何在mysql中總結日期，任何一個都有幫助？
需要php來完成這些工作嗎？

select ? from table where ? 

Answer 1

SELECT customers_id, SUM(customers_id) as sum_days FROM table GROUP BY customers_id, DAY(date); 

應該這樣做。

Answer 2

這是我的猜測：

SELECT `customers_id`, COUNT(DISTINCT(`date`)) as sum_days 
FROM `table` GROUP BY `customers_id` 

我試圖在一個小桌子，我擺弄並得到了以下幾點：

SELECT author, entry_date FROM table; 
+--------+------------+ 
| author | entry_date | 
+--------+------------+ 
|  5 | 0000-00-00 | 
|  8 | 0000-00-00 | 
|  8 | 0000-00-00 | 
|  8 | 2013-02-28 | 
|  8 | 2013-02-28 | 
|  8 | 2013-03-02 | 
+--------+------------+ 

田田

SELECT author, COUNT(DISTINCT(entry_date)) as num_days 
FROM table GROUP BY author ; 
+--------+----------+ 
| author | num_days | 
+--------+----------+ 
|  5 |  1 | 
|  8 |  3 | 
+--------+----------+ 
2 rows in set (0.00 sec) 

此外，這是前一個回覆在我的同桌上的結果：

SELECT author, SUM(author) as sum_days FROM table 
GROUP BY author, DAY(entry_date); 
+--------+----------+ 
| author | sum_days | 
+--------+----------+ 
|  5 |  5 | 
|  8 |  16 | 
|  8 |  8 | 
|  8 |  16 | 
+--------+----------+ 
4 rows in set (0.00 sec)