如何将两个MySQL列合并为一列？

Question

我想转换这个MySQL表:

title1 | title2 |type  
-------+--------+----
qwe1   | qwe2   | 3  
asd1   | asd2   | 7

在PHP中使用此表

title | type  
------+-----
asd1  | 7  
asd2  | 7  
qwe1  | 3  
qwe1  | 3

但我不知道如何正确地按第一列排序PHP表.

(这是我目前使用的代码)

$sql = "SELECT * FROM table ORDER BY title1, title2";   
$pager = new PS_Pagination( $dbh, $sql, 3, 4, null );//pagination class
$rs = $pager->paginate(); 

while ($row = $rs->fetch(PDO::FETCH_ASSOC)){
    echo "<tr>";
    echo "<td>{$row['title1']}</td>";
    echo "<td>{$row['type']}</td>";
    echo "</tr>";

    echo "<tr>";
    echo "<td>{$row['title2']}</td>";
    echo "<td>{$row['type']}</td>";
    echo "</tr>";
}       

echo "</table>";

Answer 1

在SQL本身,您可以使用它UNION.并ORDER BY用于整个查询!

SELECT `title1` AS `title`, `type`
FROM `table`
UNION
SELECT `title2` AS `title`, `type`
FROM `table`
ORDER BY `title` ASC

产量

+-------+------+
| TITLE | TYPE |
+-------+------+
|  asd1 |    7 |
|  asd2 |    7 |
|  qwe1 |    3 |
|  qwe2 |    3 |
+-------+------+

小提琴:http://sqlfiddle.com/#!2/fff9cf/1

Answer 2

尝试:

SELECT 'title1' AS 'title', 'type' from 'table'
UNION
SELECT 'title2' AS 'title', 'type' from 'table'
ORDER BY 'title'

希望我的语法正确.

基本上你想做两个查询并合并结果,这是UNION所做的.

编辑(请参阅UNION和UNION ALL之间差异的其他答案).

Answer 3

我认为你需要使用 UNION：

SELECT title1, type
FROM YourTable
UNION ALL
SELECT title2, type
FROM YourTable

如果您不想重复，可以使用 UNION 而不是 UNION ALL 来删除。

- 编辑

正如所建议的，如果您也打算对这些结果进行排序，只需添加一个 ORDER BY 子句并为您的列指定别名：

SELECT title1 title, type
FROM YourTable
UNION ALL
SELECT title2 title, type
FROM YourTable
ORDER BY title

祝你好运。