棘手的MySQL查詢的日期時間

Question

我有一個日期時間查詢工作qreat：

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

唯一的問題是我無法弄清楚如何/我是否可以填寫日期與零個結果爲零或爲空。

ie;如果2011-08-25有5條記錄，2011-08-27有7條記錄，我希望結果返回5,0,7或5，null，7

任何幫助將不勝感激！

Answer 1

您可以使用天數創建附加表並連接兩個表。這裏是一個例子，它適用於指定的月份 -

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