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1.查找重复的行
select * from blog_user_relation a where (a.account_instance_id,a.follow_account_instance_id) in (select account_instance_id,follow_account_instance_id from blog_user_relation group by account_instance_id, follow_account_instance_id having count(*) > 1)
2.删除重复的行(保留一条)
ps:因为mysql的delete,如果被删的表的where条件里有in,且in里面也有此表,那就删除不了。
/*创建个临时表*/ create table blog_user_relation_temp as ( select * from blog_user_relation a where (a.account_instance_id,a.follow_account_instance_id) in ( select account_instance_id,follow_account_instance_id from blog_user_relation group by account_instance_id, follow_account_instance_id having count(*) > 1) and relation_id not in (select min(relation_id) from blog_user_relation group by account_instance_id, follow_account_instance_id having count(*)>1)); /*删除数据*/ delete from `blog_user_relation` where relation_id in (select relation_id from blog_user_relation_temp); /*删除临时表*/ drop table blog_user_relation_temp;
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