flask and flask_sqlalchemy and flask_apscheduler

todo

flask

flask add_url_rule vs @app.route()
g
request

app.app_context

sqlalchemy

db.create_all() can create table
db.drop_all() can delete table

sql

flask sqlalchemy execute raw sql
db.engine.execute()
what is db.session
db.session.add
db.session.commit

apscheduler

how to use it?