将mysql列合并到行

Question

我有一个结构如下的表：

+-----+------------+------------+------------+------------+
| ID  |  FEATURE1  |  FEATURE2  |  FEATURE3  |  FEATURE4  |
+-----+------------+------------+------------+------------+
|  1  |  red       |  blue      |  black     |  grey      |
|  2  |  yellow    |            |            |            |
|  3  |  orange    |  red       |  green     |  golden    |
|  4  |  orange    |  grey      |  blue      |            |

我想做的是查询表并返回所有可能的功能以在自动完成调用中使用。我需要查询只返回唯一值。

SELECT (FEATURE1, FEATURE2, FEATURE3, FEATURE4, FEATURE5) FEATURE
FROM products
WHERE `FEATURE` LIKE 'gr%\'

我想要的输出是：

+----------+
| FEATURE  |
+----------+
|  green   |
|  grey    |

Answer 1

基本上，您可以使用UNION 将所有列组合在一行中。

SELECT  * 
FROM
(
    SELECT FEATURE1 FEATURE FROM TableName
    UNION
    SELECT FEATURE2 FEATURE FROM TableName
    UNION
    SELECT FEATURE3 FEATURE FROM TableName
    UNION
    SELECT FEATURE4 FEATURE FROM TableName
) sub
WHERE   FEATURE LIKE 'gr%'

• SQLFiddle Demo