mysql中如何不重复插入,mysql 重复的不插入,mysql唯一的插入

 INSERT INTO new_schedules_spider_shipsname ( ID,SCAC,VESSEL,VOYAGE,SERVICE_NAME,MD5 ) SELECT
  NULL,%s,%s,%s,%s,%s
  FROM
  DUAL 
  WHERE
NOT EXISTS ( SELECT * FROM new_schedules_spider_shipsname s WHERE s.MD5 = %s and s.STATE =0 )