我有一个如下所示的 MySQL 表:
+--------+------------+------------------+
| id | account_id | posted_at |
+--------+------------+------------------+
| 1 | 1 | 2013-10-05 23:09 |
| 2 | 1 | 2013-10-07 14:24 |
| 3 | 1 | 2013-10-07 01:17 |
| 4 | 1 | 2013-10-09 06:58 |
+--------+------------+------------------+
对于特定的 account_id
(在本例中为 1),我想返回此值(对于当月的日期):
+--------+------------+
| count | date |
+--------+------------+
| 0 | 2013-10-01 |
| 0 | 2013-10-02 |
| 0 | 2013-10-03 |
| 0 | 2013-10-04 |
| 1 | 2013-10-05 |
| 0 | 2013-10-06 |
| 2 | 2013-10-07 |
| 0 | 2013-10-08 |
| 1 | 2013-10-09 |
+--------+------------+
我有一个 SQL 查询,它返回本月内每个日期的 COUNTS。
SELECT
DATE(posted_at) AS formatted_date,
COUNT(id) AS count
FROM entries
WHERE account_id = 1
AND MONTH(DATE(posted_at)) = MONTH(NOW())
GROUP BY formatted_date
ORDER BY formatted_date ASC
它只是返回这个:
+--------+------------+
| count | date |
+--------+------------+
| 1 | 2013-10-05 |
| 2 | 2013-10-07 |
| 1 | 2013-10-09 |
+--------+------------+
当然,对于没有数据的日期,COUNT 不会返回任何内容。我希望结果对于没有数据的日期为零。
我读到您应该创建所有可能日期的联接表。这是唯一的方法吗?
最佳答案
你可以尝试这样的事情
Declare @INT DATETIME = null
SELECT COUNT( CASE WHEN @INT IS NOT NULL THEN @INT ELSE NULL END)
我不确定 mysql,但在 sql server 中它会是这样的......
SELECT
DATE(posted_at) AS formatted_date,
COUNT( CASE WHEN IS NOT NULL THEN posted_at ELSE NULL END ) AS [count]
FROM entries
WHERE account_id = 1
AND MONTH(DATE(posted_at)) = MONTH(NOW())
GROUP BY formatted_date
ORDER BY formatted_date ASC
关于MySQL 返回当月所有日期的计数,包括结果为零的日期,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/19280262/