这3个sql的执行时间怎么和书上说的不一样。

订单行40万条数据，1 in应该是最慢的， 2有临时表应该挺快的，3有临时表应该也挺快的。但是执行效果来看 1，2 ，3的时候差不多。 ```sql #0.452秒 select id,order_id from order_item where order_id in ( select order_id from order_item GROUP BY order_id HAVING count(order_id)>1) #0.763秒 select distinct o.order_id,o.id from order_item o, ( select order_id from order_item GROUP BY order_id HAVING count(order_id)>1 ) as tem where tem.order_id=o.order_id ; #0.462秒 select id,order_id from order_item INNER join ( select order_id from order_item GROUP BY order_id HAVING count(order_id)>1 ) as tem USING(order_id) ; ```