我有一个表与以下字段:
id (Unique)
url (Unique)
title
company
site_id
现在，我需要删除具有相同标题、company和site_id的行。一种方法是使用下面的SQL和脚本(PHP):
SELECT title, site_id, location, id, count( * )
FROM jobs
GROUP BY site_id, company, title, location
HAVING count( * ) >1
运行此查询后，可以使用服务器端脚本删除重复项。
但是，我想知道这是否只能使用SQL查询。
当前回答
我有一个忘记在id行添加主键的表。虽然它在id上有auto_increment。但是有一天，一个东西在数据库中重放了mysql bin日志，插入了一些重复的行。
我删除重复的行
选择唯一的重复行并导出它们 选择T1。(select count(*) as c,id from table_name group by id) T2 on T1。id = T2。T2.c > 1 group by T1.id; 按id删除重复的行 从导出的数据中插入该行。 然后在id上添加主键
其他回答
MySQL对引用要删除的表有限制。你可以用一个临时表来解决这个问题，比如:
create temporary table tmpTable (id int);
insert into tmpTable
(id)
select id
from YourTable yt
where exists
(
select *
from YourTabe yt2
where yt2.title = yt.title
and yt2.company = yt.company
and yt2.site_id = yt.site_id
and yt2.id > yt.id
);
delete
from YourTable
where ID in (select id from tmpTable);
以下是Kostanos在评论中的建议: 上面唯一缓慢的查询是DELETE，适用于数据库非常大的情况。这个查询可以更快:
DELETE FROM YourTable USING YourTable, tmpTable WHERE YourTable.id=tmpTable.id
下面是我用过的方法，它很有效:
create table temp_table like my_table;
T_id是唯一的列
insert into temp_table (id) select id from my_table GROUP by t_id;
delete from my_table where id not in (select id from temp_table);
drop table temp_table;
删除表中重复的记录。
delete from job s
where rowid < any
(select rowid from job k
where s.site_id = k.site_id and
s.title = k.title and
s.company = k.company);
or
delete from job s
where rowid not in
(select max(rowid) from job k
where s.site_id = k.site_id and
s.title = k.title and
s.company = k.company);
我找到了一个简单的方法。(保持最新的)
DELETE t1 FROM table_name t1 INNER JOIN table_name t2
WHERE t1.primary_id < t2.primary_id
AND t1.check_duplicate_col_1 = t2.check_duplicate_col_1
AND t1.check_duplicate_col_2 = t2.check_duplicate_col_2
...
一种简单易懂且不需要主键的解决方案:
add a new boolean column alter table mytable add tokeep boolean; add a constraint on the duplicated columns AND the new column alter table mytable add constraint preventdupe unique (mycol1, mycol2, tokeep); set the boolean column to true. This will succeed only on one of the duplicated rows because of the new constraint update ignore mytable set tokeep = true; delete rows that have not been marked as tokeep delete from mytable where tokeep is null; drop the added column alter table mytable drop tokeep;
我建议您保留您添加的约束，以便将来防止出现新的重复。
