（sql笔记）如何查重

如何在数据量大的时候找到重复的数据？

select  id,SchemeId as s from orderaction
GROUP BY SchemeId
HAVING COUNT(s)>1

***要是上面看不懂，可以添加count()函数计数***

select  id,count(SchemeId) as s from orderaction
GROUP BY SchemeId
HAVING COUNT(s)>1