各字段解释
https://www.cnblogs.com/fengff/p/9317051.html
https://segmentfault.com/a/1190000017249661?utm_source=tag-newest(这个比较好)
https://blog.csdn.net/choumin/article/details/89513943
中文手册
http://www.pythondoc.com/flask-sqlalchemy/quickstart.html#id3
使用unix_socket连接的方法
SQLALCHEMY_DATABASE_URI = "mysql+cymysql://root:root@localhost:3306/lucax?unix_socket=/Applications/MAMP/tmp/mysql/mysql.sock"