sql - MySQL 查询：如何做到这一点？

Question

我知道这张桌子不是它应该的样子，但它就是它，它不能改变。

我的表：

|carID  | car1      | car2      | car3      |
-------------------------------------------------
|   1   | someCar 1 | someCar 2 | someCar 3 |
-------------------------------------------------

我想要以下结果，就像它应该在关系表中一样：

|carID  |car        |
---------------------
|1      | someCar 1 |
|1      | someCar 2 |
|1      | someCar 3 |

有人知道该怎么做吗？

我试过这样的事情：

SELECT carId, car1, car2, car3 FROM cars WHERE carId = '1' GROUP BY car1, car2, car3

Answer 1

UNION

SELECT   CarID, car1 car FROM MyTable
UNION ALL
SELECT   CarID, car2 car FROM MyTable
UNION ALL
SELECT   CarID, car3 car FROM MyTable

Answer 2

尝试UNION ALL：

SELECT CarID, Car1 FROM myTable WHERE carID='1'
UNION ALL
SELECT CarID, Car2 FROM myTable WHERE carID='1'
UNION ALL
SELECT CarID, Car3 FROM myTable WHERE carID='1'

Answer 3

创建三个选择的并集：

SELECT carID, car1 FROM cars WHERE carID = '1'
UNION ALL
SELECT carID, car2 FROM cars WHERE carID = '1'
UNION ALL
SELECT carID, car3 FROM cars WHERE carID = '1'

请注意，您需要使用UNION ALL，而不仅仅是UNION，因为UNION单独使用会遗漏重复项。例如，如果car2和car3相同，则结果将仅包含两条记录。