MySQL，根据列值从其他行中选择

Question

我有下表

---------------------------
|ID  |Image      | link    |
|01  |           | 02      |  
|02  |steve.jpg  |         |         
|03  |eric.jpg   |         |         
----------------------------

链接字段存储ID，因此我可以设置两行之间的关系。

ID 01的链接字段设置为02。因此，我希望ID 01使用该字段中设置了ID的图像，因此它将为steve.jpg。

如何获取所有行，以使带有链接字段的行以该图像结尾？

Answer 1

您可以使用自我连接以显示链接ID的图像名称

select t.*,t1.Image as link_image
from t 
left join t t1 on(t.link = t1.ID)

演示

Answer 2

SELECT a.id, b.image, a.link
FROM YourTable AS a
JOIN YourTable AS b ON a.link = b.id
UNION
SELECT id, image, link
FROM YourTable
WHERE link IS NULL

Answer 3

像这样：

(SELECT ID, Image from mytable WHERE link = '' )
UNION ALL
(SELECT m1.ID as ID, m2.Image as Image 
   FROM mytable AS m1 INNER JOIN mytable AS m2 ON ( m1.link=m2.ID )
)