通过用户模型，对数据库进行增删改查操作。

增加：
db.session.add(user)
db.session.commit()

查询：
User.query.filter(User.username == 'mis1114').first()

修改：
user.password = '111111'
db.session.commit()

删除：
db.session.delete(user)
db.session.commit()

from flask import Flask, render_template
from flask_sqlalchemy import SQLAlchemy
import config

app = Flask(__name__)
app.config.from_object(config)
db = SQLAlchemy(app)

class User(db.Model):
    __tablename__='user'
    id = db.Column(db.Integer,primary_key=TabError,autoincrement=True)
    username = db.Column(db.String(20),nullable=False)
    password = db.Column(db.String(20), nullable=False)
    nickname = db.Column(db.String(20))

# 查询删除
user = User.query.filter(User.username == 'lin').first()
db.session.delete(user)
db.session.commit()

# 修改
user.password = '1234'
print(user.username,user.password)
db.session.commit()

# 增加
user = User(username = 'lin',password = 'lin')
db.session.add(user)
db.session.commit()