How To Find Duplicate Values in MySQL SELECT mem_name, COUNT(mem_name) FROM mem_password GROUP BY mem_name HAVING COUNT(mem_name) > 1       ***************************************************************************************************************** compare row number and value form two different table SELECT COUNT(member_info.mem_name) as milon, mess_info.mess_mem_num,mess_info.mess_name FROM member_info INNER join mess_info on mess_info.mess_name=member_info.mess_name GROUP BY member_info.mess_name

Insert – Subquery returns more then 1 row

Insert – Subquery returns more then 1 row Reference:   INSERT INTO mem_password ( `mem_name` , `password`, `hash_password`) SELECT mem_name , ‘No password’,’f8cf7801bd44f47bdf08e4ab122ab5bc’ FROM member_info AS a WHERE NOT EXISTS ( SELECT * FROM mem_password AS b WHERE a.mem_name=b.mem_name ) and a.version=’7.2.2′ and a.mem_role!=’admin’