flask_sqlalchemy实现数据库增删改查代码

可以提供如下代码实现基本的增删改查功能：

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)

    def __repr__(self):
        return '<User %r>' % self.name

# 创建数据库表
db.create_all()

# 实现增加用户
@app.route('/add_user')
def add_user():
    new_user = User(name='John', email='john@example.com')
    db.session.add(new_user)
    db.session.commit()
    return 'New user has been added!'

# 实现查询用户
@app.route('/find_user')
def find_user():
    result = User.query.filter_by(name='John').first()
    return 'The email address of the user is ' + result.email

# 实现修改用户
@app.route('/update_user')
def update_user():
    user = User.query.filter_by(name='John').first()
    user.email = 'new_email@example.com'
    db.session.commit()
    return 'The email address of the user has been updated!'

# 实现删除用户
@app.route('/delete_user')
def delete_user():
    user = User.query.filter_by(name='John').first()
    db.session.delete(user)
    db.session.commit()
    return 'The user has been deleted!'

if __name__ == '__main__':
    app.run(debug=True)

上述代码实现了基本的增删改查功能，使用flask_sqlalchemy框架操作SQLite数据库。其中，创建了User模型类，包含id、name、email三个字段；同时也包含了增加用户、查询用户、修改用户、删除用户四个接口。在实现上述功能之前，需要先安装相应的依赖包，如需使用MySQL需要另行配置数据库连接信息。