Flask学习回顾（八）

数据库查询：

In [1]: from Flask_SQLalchemy_demo import *

In [2]: User.query.all()
Out[2]: 
[<User: wang 1 wang@163.com 123456>,
 <User: zhang 2 zhang@189.com 201512>,
 <User: chen 3 chen@126.com 987654>,
 <User: zhou 4 zhou@163.com 456789>,
 <User: tang 5 tang@itheima.com 158104>,
 <User: wu 6 wu@gmail.com 5623514>,
 <User: qian 7 qian@gmail.com 1543567>,
 <User: liu 8 liu@itheima.com 867322>,
 <User: li 9 li@163.com 4526342>,
 <User: sun 10 sun@163.com 235523>]

In [3]: User.query.count()
Out[3]: 10

In [4]: User.query.first()
Out[4]: <User: wang 1 wang@163.com 123456>

In [5]: User.query.get(4)
Out[5]: <User: zhou 4 zhou@163.com 456789>

In [6]: User.query.filter_by(id=4).first()
Out[6]: <User: zhou 4 zhou@163.com 456789>

In [7]: User.query.filter(User.id==4).first()
Out[7]: <User: zhou 4 zhou@163.com 456789>

对比：
filter_by: 属性=
filter: 对象.属性==
filter功能更强大，可以实现更多的一些查询，支持比较运算符