Question

我可以产生这个输出：

+----------+------------+------------+------------+
| startt   | 2013-04-01 | 2013-04-02 | 2013-04-03 |
+----------+------------+------------+------------+
| 08:00:00 | Donald     | Daisy      | Mickey     |
| 12:00:00 | Pluto      | Goofy      | Minnie     |
| 14:00:00 | NULL       | Mickey     | NULL       |
+----------+------------+------------+------------+

来自这个原始数据：

mysql> select * from test;
+------------+----------+----------+--------+
| startd     | startt   | duration | name   |
+------------+----------+----------+--------+
| 2013-04-01 | 08:00:00 |        4 | Donald |
| 2013-04-02 | 08:00:00 |        4 | Daisy  |
| 2013-04-03 | 08:00:00 |        4 | Mickey |
| 2013-04-03 | 12:00:00 |        4 | Minnie |
| 2013-04-01 | 12:00:00 |        4 | Pluto  |
| 2013-04-02 | 12:00:00 |        4 | Goofy  |
| 2013-04-02 | 14:00:00 |        4 | Mickey |
+------------+----------+----------+--------+
mysql>

使用此MySQL动态查询：

1 set @sql = null;
2 select
3     group_concat(distinct
4         concat(
5             'group_concat(case when startd = ''',
6             `startd`,
7             ''' then `name` end ) as `',
8             `startd`,'`'
9         )
10     ) into @sql
11 from test;
12
13 set @sql = concat('select startt, ',@sql,'
14                     from test
15                     group by startt');
16
17 prepare stmt from @sql;
18 execute stmt;
19 deallocate prepare stmt;

感谢您对此问题的帮助@ hims056。

如何将此动态查询的结果传递给我可以在PHP中循环的变量？

过去我用过：

$result=mysqli_query($con,"select ...");
... lines deleted ...
while ($row=mysqli_fetch_array($result))
... lines deleted ...

在这些情况下，这种方法似乎不合适。

任何帮助都将不胜感激。

Answer 1

可能的解决方案是将其包装在存储过程中

DELIMITER $$
CREATE PROCEDURE sp_test()
    BEGIN
    SET @sql = NULL;
    SELECT
        GROUP_CONCAT(DISTINCT
            CONCAT(
                'GROUP_CONCAT(CASE WHEN startd = ''',
                `startd`,
                ''' THEN `name` END ) AS `',
                `startd`,'`'
             )
         ) INTO @sql
     FROM test;

     SET @sql = CONCAT('SELECT startt, ', @sql, '
                          FROM test
                         GROUP BY startt');

    PREPARE stmt FROM @sql;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
END$$
DELIMITER ;

并使用它

CALL sp_test();

这是 SQLFiddle 演示

UPDATE：在php端你可以做到

$db = new mysqli('localhost', 'user', 'password', 'dbname');
$sql = "CALL sp_test()";
$query = $db->query($sql);
$result = array();
while ($row = $query->fetch_assoc()) {
    $result[] = $row;
}
$query->close();
$db->close();
// then do whatever you need to do to present it
var_dump($result);

为简洁起见，故意省略了所有错误处理

如何在PHP中实现mySQL动态查询？

1 个答案: