我正在尝试使用GROUP BY子句创建SELECT语句,该子句应返回“默认值”.

想象一下以下简单的MySQL表：

CREATE TABLE `tracker` (
  `id` INTEGER PRIMARY KEY auto_increment,`date` DATETIME NOT NULL,`customer_id` INTEGER NOT NULL
);

该表只包含一条记录：

INSERT INTO `tracker` (`date`,`customer_id`) VALUES('2010-05-03',1);

在病房之后,我正在执行以下SQL查询：

SELECT DATE(`date`),COUNT(customer_id) FROM tracker
WHERE DATE(`date`) >= '2010-05-01' AND DATE(`date`) <= '2010-05-05'
GROUP BY DATE(`date`) ORDER BY DATE(`date`);

并获得预期的结果集：

+----+---------------------+-------------+
| id | date                | customer_id |
+----+---------------------+-------------+
|  1 | 2010-05-10 00:00:00 |           1 |
+----+---------------------+-------------+

但是,我希望结果集看起来像这样：

+--------------+--------------------+
| DATE(`date`) | COUNT(customer_id) |
+--------------+--------------------+
| 2010-05-01   |                  0 |
| 2010-05-02   |                  0 |
| 2010-05-03   |                  1 |
| 2010-05-04   |                  0 |
| 2010-05-05   |                  0 |
+--------------+--------------------+

有可能实现这种行为吗？