棘手的MySQL查询的日期时间

Question

我有一个日期时间查询工作qreat：

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

唯一的问题是我无法弄清楚如何/我是否可以填写日期与零个结果为零或为空。

ie;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！

Answer 1

您可以使用天数创建附加表并连接两个表。这里是一个例子，它适用于指定的月份 -

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 | 
+--------+------------------+