谁能解释一下这条语句的执行过程
select * from customers c where 3<=(select count(*) from order1 o where c.ID=o.cus_ID)
2007-02-23 20:25
2007-02-25 20:52
2007-03-01 20:49
2007-03-01 22:48
2007-03-08 22:34