1.查询单列重复(table：表名，name 字段名)：
select * from table
where name in (select name from table group by name having count
(name) > 1)
2.查询多列重复(table：表名，name 字段名，code字段名)：
SELECT a.* FROM table a,(
SELECT name,code
FROM table
GROUP BY name,code
HAVING COUNT(1)>1
) AS b
WHERE a.name=b.name AND a.code=b.code