这个SQL DELETE FROM语法有什么问题？

Question

我正在尝试删除96k记录。

删除表xoops_bb_posts_text页面中没有匹配的post_id到xoops_bb_posts的所有记录

此查询有效返回91k记录：

SELECT *  
   FROM xoops_bb_posts_text t  
   WHERE not exists (
       select post_id 
           from xoops_bb_posts p 
           WHERE p.post_id = t.post_id 
   );  

当我尝试删除这些记录时出现语法错误，但我没有看到它。

DELETE FROM xoops_bb_posts_text t  
WHERE not exists (
    select post_id 
       from xoops_bb_posts p 
    WHERE p.post_id = t.post_id 
);  

错误在哪里？

错误

SQL查询：文档

DELETE FROM xoops_bb_posts_text t 
   WHERE NOT EXISTS (  
      SELECT post_id  
         FROM xoops_bb_posts p  
         WHERE p.post_id = t.post_id  
)  

MySQL说：文档

  

＃1064 - 您的SQL语法出错;检查手册   对应于您的MySQL服务器版本，以便使用正确的语法   在'WHERE not exists附近'（从xoops_bb_posts中选择post_id p WHERE   p.post_id = t.post_'在第2行

Answer 1

如果在删除调用中对别名进行别名，则必须使用别名作为参数：

DELETE alias FROM tablerealname as ALIAS ...

所以在OP的原始问题中，他只需在DELETE之后添加别名：

DELETE t FROM xoops_bb_posts_text as t WHERE NOT EXISTS (  
SELECT post_id  
FROM xoops_bb_posts as p  
WHERE p.post_id = t..post_id  
)  

Answer 2

对我来说，通过使用带有delete的{​​{1}}语句并查找不匹配的行，可以更轻松地解决此问题。像这样：

outer join

或只是更改您的查询：

delete t from xoops_bb_posts_text as t
left outer join xoops_bb_posts as p
on p.post_id = t.post_id
where p.post_id is null;

Answer 3

您不能在单表DELETE in MySql中对表名进行别名。您需要使用完整的表名，如下所示：

DELETE FROM xoops_bb_posts_text
WHERE not exists (select post_id from xoops_bb_posts p WHERE p.post_id = xoops_bb_posts_text.post_id );

Answer 4

您无法在delete语句中指定表别名。

Answer 5

来自我的评论：

DELETE FROM xoops_bb_posts_text t  
 WHERE NOT EXISTS (
    SELECT * 
      FROM xoops_bb_posts p 
     WHERE p.post_id = t.post_id 
);  

Answer 6

CREATE TABLE IF NOT EXISTS `tbl_student1` (
  `stud_id` int(11) NOT NULL AUTO_INCREMENT,
  `stud_name` varchar(255) CHARACTER SET utf8 NOT NULL,
  `stream_id` int(11) NOT NULL,
  `address` varchar(255) CHARACTER SET utf8 NOT NULL,
  `s_date` datetime NOT NULL,
  `status` int(11) NOT NULL,
  PRIMARY KEY (`stud_id`),
  FOREIGN KEY ('stream_id')
        REFERENCES tbl_stream ('stream_id')
        ON DELETE CASCADE
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=1 ;

Answer 7

我不知道语法“EXISTS”。我认为最好使用“in”和“not in”

尝试：

DELETE FROM xoops_bb_posts_text WHERE post_id not in (SELECT post_id  FROM xoops_bb_posts)