[英]How to delete duplicates in SQL table based on multiple fields
I have a table of games, which is described as follows:我有一个游戏表,描述如下:
+---------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| date | date | NO | | NULL | |
| time | time | NO | | NULL | |
| hometeam_id | int(11) | NO | MUL | NULL | |
| awayteam_id | int(11) | NO | MUL | NULL | |
| locationcity | varchar(30) | NO | | NULL | |
| locationstate | varchar(20) | NO | | NULL | |
+---------------+-------------+------+-----+---------+----------------+
But each game has a duplicate entry in the table somewhere, because each game was in the schedules for two teams.但是每场比赛在表中的某处都有重复的条目,因为每场比赛都在两支球队的赛程中。 Is there a sql statement I can use to look through and delete all the duplicates based on identical date, time, hometeam_id, awayteam_id, locationcity, and locationstate fields?
是否有一个 sql 语句可以用来查看和删除基于相同日期、时间、hometeam_id、awayteam_id、locationcity 和 locationstate 字段的所有重复项?
You should be able to do a correlated subquery to delete the data.您应该能够执行相关子查询来删除数据。 Find all rows that are duplicates and delete all but the one with the smallest id.
查找所有重复的行并删除除 id 最小的行之外的所有行。 For MYSQL, an inner join (functional equivalent of EXISTS) needs to be used, like so:
对于 MYSQL,需要使用内部联接(功能等效于 EXISTS),如下所示:
delete games from games inner join
(select min(id) minid, date, time,
hometeam_id, awayteam_id, locationcity, locationstate
from games
group by date, time, hometeam_id,
awayteam_id, locationcity, locationstate
having count(1) > 1) as duplicates
on (duplicates.date = games.date
and duplicates.time = games.time
and duplicates.hometeam_id = games.hometeam_id
and duplicates.awayteam_id = games.awayteam_id
and duplicates.locationcity = games.locationcity
and duplicates.locationstate = games.locationstate
and duplicates.minid <> games.id)
To test, replace delete games from games
with select * from games
.为了测试,用
select * from games
替换delete games from games
select * from games
。 Don't just run a delete on your DB :-)不要只是在您的数据库上运行删除 :-)
You can try such query:您可以尝试这样的查询:
DELETE FROM table_name AS t1
WHERE EXISTS (
SELECT 1 FROM table_name AS t2
WHERE t2.date = t1.date
AND t2.time = t1.time
AND t2.hometeam_id = t1.hometeam_id
AND t2.awayteam_id = t1.awayteam_id
AND t2.locationcity = t1.locationcity
AND t2.id > t1.id )
This will leave in database only one example of each game instance which has the smallest id.这将在数据库中只留下一个具有最小 id 的游戏实例的示例。
The best thing that worked for me was to recreate the table.对我有用的最好的事情是重新创建表格。
CREATE TABLE newtable SELECT * FROM oldtable GROUP BY field1,field2;
You can then rename.然后您可以重命名。
To get list of duplicate entried matching two fields获取匹配两个字段的重复条目列表
select t.ID, t.field1, t.field2
from (
select field1, field2
from table_name
group by field1, field2
having count(*) > 1) x, table_name t
where x.field1 = t.field1 and x.field2 = t.field2
order by t.field1, t.field2
And to delete all the duplicate only并只删除所有重复项
DELETE x
FROM table_name x
JOIN table_name y
ON y.field1= x.field1
AND y.field2 = x.field2
AND y.id < x.id;
select orig.id,
dupl.id
from games orig,
games dupl
where orig.date = dupl.date
and orig.time = dupl.time
and orig.hometeam_id = dupl.hometeam_id
and orig. awayteam_id = dupl.awayeam_id
and orig.locationcity = dupl.locationcity
and orig.locationstate = dupl.locationstate
and orig.id < dupl.id
this should give you the duplicates;这应该给你重复; you can use it as a subquery to specify IDs to delete.
您可以将其用作子查询来指定要删除的 ID。
只要您没有在选择查询中获得表的 id(主键)并且其他数据完全相同,您就可以使用SELECT DISTINCT
来避免获得重复的结果。
delete from games
where id not in
(select max(id) from games
group by date, time, hometeam_id, awayteam_id, locationcity, locationstate
);
Workaround解决方法
select max(id) id from games
group by date, time, hometeam_id, awayteam_id, locationcity, locationstate
into table temp_table;
delete from games where id in (select id from temp);
DELETE FROM tbl
USING tbl, tbl t2
WHERE tbl.id > t2.id
AND t2.field = tbl.field;
in your case:在你的情况下:
DELETE FROM games
USING games tbl, games t2
WHERE tbl.id > t2.id
AND t2.date = tbl.date
AND t2.time = tbl.time
AND t2.hometeam_id = tbl.hometeam_id
AND t2.awayteam_id = tbl.awayteam_id
AND t2.locationcity = tbl.locationcity
AND t2.locationstate = tbl.locationstate;
reference: https://dev.mysql.com/doc/refman/5.7/en/delete.html参考: https : //dev.mysql.com/doc/refman/5.7/en/delete.html
DELETE FROM table
WHERE id =
(SELECT t.id
FROM table as t
JOIN (table as tj ON (t.date = tj.data
AND t.hometeam_id = tj.hometeam_id
AND t.awayteam_id = tj.awayteam_id
...))
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