MySQL 棘手的日期时间查询答案

【问题标题】：MySQL tricky datetime queryMySQL 棘手的日期时间查询
【发布时间】：2011-08-25 05:23:57
【问题描述】：

我有一个适用于 qreat 的日期时间查询：

$q="SELECT COUNT(blocked) AS sum_blocked, DATE(created) AS date_label ".
   "FROM sms_subscribers WHERE blocked=0 GROUP BY DATE(created)";

唯一的问题是我不知道如何/如果我可以用零或空值填充零结果的日期。

即;如果 2011-08-25 有 5 条记录，2011-08-27 有 7 条记录，我希望结果返回 5、0、7 或 5、null、7

任何帮助将不胜感激！

【问题讨论】：

标签： mysql date group-by fill

【解决方案1】：

您可以创建一个带有天数的附加表并连接两个表。这是一个例子，它适用于指定月份 -

CREATE TABLE days (
  number INT(11) NOT NULL
);

CREATE TABLE sms_subscribers (
  id INT(11) NOT NULL AUTO_INCREMENT,
  created DATETIME DEFAULT NULL,
  PRIMARY KEY (id)
);

INSERT INTO days VALUES 
  (1), (2), (3), (4), (5), (6), (7), (8), (9), (10),
  (11), (12), (13), (14), (15), (16), (17), (18), (19), (20),
  (21), (22), (23), (24), (25), (26), (27), (28), (29), (30), (31);

INSERT INTO sms_subscribers VALUES 
  (1, '2011-08-25 08:35:27'),
  (2, '2011-08-11 08:35:30'),
  (3, '2011-08-06 08:35:35'),
  (4, '2011-06-06 08:35:40'),
  (5, '2011-06-19 08:35:47'),
  (6, '2011-06-01 08:35:53'),
  (7, '2011-08-28 08:36:02'),
  (8, '2011-08-25 08:57:58');


SELECT d.number, COUNT(t.created) FROM days d
  LEFT JOIN (SELECT * FROM sms_subscribers
              WHERE YEAR(created) = 2011 AND MONTH(created) = 8) t -- Specify year and monts here
    ON DAYOFMONTH(t.created) = d.number
WHERE
  d.number <= DAYOFMONTH(LAST_DAY('2011-08-01')) -- Specify any day in the specified month, it will help to found out max number of days in the month
GROUP BY d.number;

+--------+------------------+
| number | COUNT(t.created) |
+--------+------------------+
|      1 |                0 |
|      2 |                0 |
|      3 |                0 |
|      4 |                0 |
|      5 |                0 |
|      6 |                1 |
|      7 |                0 |
|      8 |                0 |
|      9 |                0 |
|     10 |                0 |
|     11 |                1 |
|     12 |                0 |
|     13 |                0 |
|     14 |                0 |
|     15 |                0 |
|     16 |                0 |
|     17 |                0 |
|     18 |                0 |
|     19 |                0 |
|     20 |                0 |
|     21 |                0 |
|     22 |                0 |
|     23 |                0 |
|     24 |                0 |
|     25 |                2 |
|     26 |                0 |
|     27 |                0 |
|     28 |                1 |
|     29 |                0 |
|     30 |                0 |
|     31 |                0 |
+--------+------------------+

【讨论】：

太棒了——这似乎工作得很好！不过，我确实对其进行了调整以循环使用几个月。