mysql数据库关系表设计原则

三范式
https://blog.csdn.net/qq_36432666/article/details/78934073

https://kb.cnblogs.com/page/138526/

http://blog.sina.com.cn/s/blog_a29f7cb50101jr5d.html

https://www.cnblogs.com/mjbrian/p/6841226.html

https://blog.csdn.net/persistencequxi/article/details/78502501

SQL 表设置原则例子
https://blog.csdn.net/yerenyuan_pku/article/details/52260359

https://blog.csdn.net/henjuewang/article/details/84233250    个人博客系统
https://blog.csdn.net/bieleyang/article/details/77149954
https://zhangjia.io/852.html
https://juejin.im/post/5c96421e6fb9a070f12583bf#heading-14
E-R图基础练习
https://www.cnblogs.com/zpfbuaa/p/5256187.html

外键约束联动
https://www.cnblogs.com/yy20141204bb/p/8405000.html

mysql 多对多 联接查询 app_projecks user_projeck_manage app_users

   select u.userid, u.username, prj.*    from app_projecks prj inner join user_projeck_manage u_p on prj.projeck_id=u_p.projeck_id              inner join app_users u on u.userid=u_p.userid and u.userid='指定ID条件'';