Mysql一些复杂的sql语句(查询与删除重复的行)

SELECT  FROM blog_user_relation a WHERE (a.aount_instance_id,a.follow_aount_instance_id) 
IN (SELECT aount_instance_id,follow_aount_instance_id FROM blog_user_relation GROUP BY aount_instance_id, follow_aount_instance_id HAVING
 COUNT() > 1)

/创建个临时表/
CREATE TABLE blog_user_relation_temp AS
(
 SELECT  FROM blog_user_relation a WHERE 
 (a.aount_instance_id,a.follow_aount_instance_id) 
 IN ( SELECT aount_instance_id,follow_aount_instance_id FROM blog_user_relation GROUP BY aount_instance_id, follow_aount_instance_id HAVING COUNT() > 1)
 AND 
 relation_id 
 NOT IN (SELECT MIN(relation_id) FROM blog_user_relation GROUP BY aount_instance_id, follow_aount_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;