mysql 删除单表内多个字段重复的数据

DELETE from lot_log_payflow WHERE (pay_no,sub_flow_type) in   
(SELECT pay_no,sub_flow_type from (SELECT pay_no,sub_flow_type FROM lot_log_payflow GROUP BY pay_no,sub_flow_type HAVING COUNT(*)>1) s1)   
AND  
id NOT in (SELECT id from (SELECT id FROM lot_log_payflow GROUP BY pay_no, sub_flow_type HAVING COUNT(*)>1) s2);