有订单表orders,包含字段用户信息userid,字段产品信息productid,以下语句能够返回至少被订购过两次的productid?()
select productid from orders where count(productid)>1
select productid from orders where max(productid)>1
select productid from orders where having count(productid)>1 group by productid
select productid from orders group by productid having count(productid)>1