Question

我试图通过php从日期列表中获取平均天数，但我在网上找不到任何内容，所以我想我会在这里试试。以下是我目前为我输出的msyql。

我的代码来获取日期：

$result = mysql_query($query,$db) or die(mysql_error());
  while($row = mysql_fetch_array($result)) {

      echo $row['date']."<br>";

  }

我正在尝试获得每次输出之间的平均天数....非常感谢我能获得的任何帮助！

Answer 1

DROP TABLE IF EXISTS my_table;

CREATE TABLE my_table
(dt DATE NOT NULL PRIMARY KEY);

INSERT INTO my_table VALUES
('2016-01-28'),
('2016-01-27'),
('2016-01-20'),
('2015-12-28'),
('2015-12-12'),
('2015-12-05'),
('2015-12-01'),
('2015-11-27'),
('2015-11-21'),
('2015-11-11'),
('2015-11-03'),
('2015-10-31'),
('2015-10-27'),
('2015-10-17'),
('2015-10-05'),
('2015-09-20'),
('2015-09-14'),
('2015-09-02'),
('2015-08-26'),
('2015-08-18'),
('2015-08-14'),
('2015-08-08'),
('2015-07-29'),
('2015-07-18'),
('2015-07-08'),
('2015-06-22'),
('2015-06-18'),
('2015-06-07'),
('2015-05-15'),
('2015-05-13'),
('2015-05-12'),
('2015-05-02');

SELECT x.*
     , DATEDIFF(MIN(y.dt),x.dt) diff 
  FROM my_table x 
  JOIN my_table y 
    ON y.dt > x.dt 
 GROUP 
    BY x.dt;
+------------+------+
| dt         | diff |
+------------+------+
| 2015-05-02 |   10 |
| 2015-05-12 |    1 |
| 2015-05-13 |    2 |
| 2015-05-15 |   23 |
| 2015-06-07 |   11 |
| 2015-06-18 |    4 |
| 2015-06-22 |   16 |
| 2015-07-08 |   10 |
| 2015-07-18 |   11 |
| 2015-07-29 |   10 |
| 2015-08-08 |    6 |
| 2015-08-14 |    4 |
| 2015-08-18 |    8 |
| 2015-08-26 |    7 |
| 2015-09-02 |   12 |
| 2015-09-14 |    6 |
| 2015-09-20 |   15 |
| 2015-10-05 |   12 |
| 2015-10-17 |   10 |
| 2015-10-27 |    4 |
| 2015-10-31 |    3 |
| 2015-11-03 |    8 |
| 2015-11-11 |   10 |
| 2015-11-21 |    6 |
| 2015-11-27 |    4 |
| 2015-12-01 |    4 |
| 2015-12-05 |    7 |
| 2015-12-12 |   16 |
| 2015-12-28 |   23 |
| 2016-01-20 |    7 |
| 2016-01-27 |    1 |
+------------+------+

那么平均值就是差异的平均值，所以：

SELECT AVG(diff)
  FROM
     ( SELECT x.*
            , DATEDIFF(MIN(y.dt),x.dt) diff 
         FROM my_table x 
         JOIN my_table y 
           ON y.dt > x.dt 
        GROUP 
           BY x.dt
     ) a;

+-----------+
| AVG(diff) |
+-----------+
|    8.7419 |
+-----------+

PHP日期列表之间的平均日

1 个答案: