删除SQL中的重复列

Question

假设我的SQL数据库中有三列

ID | NAME | PHONE
-----------------    
 1 | JEFF | 467
 2 | JEFF | 489
 3 | JOHN | 234
 4 | JACK | 323
 5 | JEFF | 378

我想编写一个SQL查询,删除删除每个双NAME列的所有列.这意味着在运行SQL查询后,表应如下所示:

ID | NAME | PHONE
-----------------
 1 | JEFF | 467
 2 | JOHN | 234
 3 | JACK | 323

非常感谢你提前!

非常感谢,我现在把它改成了这个

delete from product_list y
    where exists (select 1 from product_list y2 where y.model = y2.model and y2.linkid < y.linkid);

但我总是得到这个错误:

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'delete * from product_list y where exists (select 1 from product_list y2 whe' at line 3

提前致谢!

Answer 1

标准的SQL方法是:

delete from yourtable y
    where exists (select 1 from yourtable y2 where y.name = y2.name and y2.id < y.id);

也就是说,删除存在具有相同名称和较低ID的记录的所有记录.

如果您只想返回行,请使用相同的想法:

select y.*
from yourtable y
where not exists (select 1 from yourtable y2 where y.name = y2.name and y2.id < y.id);