mysql查看数据表是否有重复数据

我们可以用



 select * from people  where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)  
select * from Users where UserId in (select UserId from Users  group by UserId having count(UserId) > 1)  






不过在数据量过大的时候查询的速度会非常慢



select count(peopleId) from people 
select count(distinct peopleId) from people  







我们可以用上面两条语句的结果进行对比判断是否存在重复数据