mysql-删除SQL数据库中的重复项
作者:互联网
我需要从看起来像这样的表中删除重复项:
id post_author post_title
-----------------------------------------------------------------------------
21319 1 Youngstown State University
20535 1 Yo San University of Traditional Chinese Medicine
30268 29 Yo San University of Traditional Chinese Medicine
29747 29 Yeshiva University
21964 1 Yale University
29247 29 Yale University
29497 29 Xavier University of Louisiana
21916 1 Xavier University
29862 29 Xavier University
29860 29 Wright State University-Main Campus
20915 1 Wright State University-Lake Campus
21562 1 World Mission University
30267 29 World Mission University
基本上,如果有两个条目具有相同的post_title,则我需要删除post_title = 1的条目,但是如果post_title是唯一的,则该条目应保持不变.
如何使用SQL查询完成?
编辑:
我尝试了Mureinik建议的查询.查询如下所示:
DELETE t FROM wp_posts AS t
WHERE t.post_author = 1 AND
EXISTS (SELECT * FROM wp_posts s
WHERE t.post_title = s.post_title
AND s.post_authot != 1)
但是我得到了错误:
[Err] 1093 - You can't specify target table 't' for update in FROM clause
我究竟做错了什么?
解决方法:
您可以在post_title = 1上设置一个条件,其中一个临时表有多个post_title:
CREATE TEMPORARY TABLE t_del AS SELECT post_title
FROM t
GROUP BY post_title
HAVING count(post_title)>1;
DELETE FROM t
WHERE post_author = 1
AND post_title IN (select post_title FROM t_del) ;
标签:sql-delete,sql,mysql 来源: https://codeday.me/bug/20191120/2043042.html