下面SQL查询的说明

Below is the sql query to select the the name of all the instructors, who gets salary at least more than one instructor.(That is leave the least paid one instructor). This query is from Database System Concepts by Silberchatz, Korth. But i can't visualise how the query is used, aside one thing, that is as is necessary to do it in this way.Below is the sql query to select the the name o