1.ER图:https://wk.baidu.com/view/44d74ae8aeaad1f346933f0f?ivk_sa=1023194j
2.建表:https://www.cnblogs.com/yonyong/p/9227558.html
3.sql查询语句案例视频:https://www.jikexueyuan.com/course/2521_2.html?ss=1