mysql常用語句

1.刪除重複數據，單列，只保留id最小的一條(自增長的列id)

DELETE 
FROM  test
WHERE `name` IN ( 
	 SELECT `name`
	 FROM ( 
		SELECT `name` 
		FROM test
		GROUP BY `name` 
		HAVING count( `name` ) > 1 
	      ) a 
	) 
    AND id NOT IN (
	 SELECT id 
	 FROM ( 
		SELECT min( id ) id 
		FROM test
		GROUP BY `name`
		HAVING count( * ) > 1 
	      ) a 
	 );

2.刪除重複數據，多列，只保留id最小的一條(自增長的列id)

DELETE 
FROM test 
WHERE id IN (
	     SELECT id 
             FROM (
		   SELECT max( a.id ) id 
		   FROM test a JOIN test b ON a.`name` = b.`name` AND a.age = b.age AND a.gender = b.gender AND a.location = b.location AND a.`year` = b.`year` 
		   GROUP BY b.`name`, b.age, b.`gender`, b.location, b.`year` 
		   HAVING count( * ) > 1
		  ) a 
            );