1.查询重复值：

select code,count(*) as count from hospital group by code having count>1;

该语句查询code重复值大于1的记录

2.删除重复：

DELETE FROM hospital WHERE    id NOT IN (SELECT         dt.minno    FROM        (SELECT             MIN(id) AS minno        FROM            hospital        GROUP BY code) dt);

该语句保留id最小的记录，其余code重复的记录全部删除