Mysql SQL：如何在何处使用自引用进行过滤

这是我的SQL代码

SELECT 
    wpp.ID, wpp.post_title, wpp.guid,
    (SELECT guid FROM wp_posts  
     WHERE post_parent = (SELECT ID FROM wp_posts 
                          WHERE post_title ="Writer Thumbnail Image "+wpp.ID )) AS imgID 
FROM 
    `wp_posts` AS wpp  
WHERE 
    wpp.post_status = "publish" 
    AND wpp.post_type = "post"  
ORDER BY 
    wpp.ID DESC 
LIMIT 4

我想要where like（where post_title=“Writer Thumbnail Image 251”），但这个数字来自wpp.ID

---

我该怎么做呢？

看来您正在使用

MySQL

。在这种情况下，您可以使用：

 SELECT wpp.ID,wpp.post_title,wpp.guid,parent.guid as imgID
 from wp_posts as wpp inner join wp_posts as parent
 on wpp.post_parent =parent.ID
WHERE wpp.post_status = "publish" 
AND wpp.post_type = "post" 
and  wpp.post_title = CONCAT("Writer Thumbnail Image ",parent.ID)
ORDER BY wpp.ID DESC LIMIT 4

我不确定您是否想要：

 and  wpp.post_title = CONCAT("Writer Thumbnail Image ",parent.ID)

或

或

选择适合你的问题的

SELECT wpp.ID,wpp.post_title,wpp.guid,
(SELECT guid FROM wp_posts  WHERE post_parent = (SELECT ID FROM wp_posts WHERE post_title =CONCAT("Writer Thumbnail Image ",wpp.ID) )) AS imgID 
FROM `wp_posts` AS wpp  WHERE wpp.post_status = "publish" AND wpp.post_type = "post"  ORDER BY wpp.ID DESC LIMIT 4

这是最后的代码。这是工作

改变

WHERE post_title ="Writer Thumbnail Image "+wpp.ID

到

---

哪个数据库

+

适用于某些应用程序，其他应用程序需要

|

或函数

CONCAT

。。。SQL方言差别很大，除了泛型之外，还始终使用您使用的确切方言进行标记。@Amadan字符串串联在标准SQL中使用| |。所以使用| |，它应该会起作用。@frlan:

是的，效果很好<代码>“SQL标准”。。。（

SELECT'A'| |'B'

是

0

，而不是

'AB'

像

SELECT CONCAT（'A'，'B'）

）Hmmm.没有意识到这一点。很抱歉也许我们应该开始考虑MySQL不再调用SQL了…谢谢。我试着将（post_title=“Writer Thumbnail Image”+wpp.ID）更改为（post_title=CONCAT（“Writer Thumbnail Image”，wpp.ID）），这是有效的。谢谢你的前任。

SELECT wpp.ID,wpp.post_title,wpp.guid,
(SELECT guid FROM wp_posts  WHERE post_parent = (SELECT ID FROM wp_posts WHERE post_title =CONCAT("Writer Thumbnail Image ",wpp.ID) )) AS imgID 
FROM `wp_posts` AS wpp  WHERE wpp.post_status = "publish" AND wpp.post_type = "post"  ORDER BY wpp.ID DESC LIMIT 4

WHERE post_title ="Writer Thumbnail Image "+wpp.ID

WHERE post_title =CONCAT("Writer Thumbnail Image ",wpp.ID)