Flask中数据库的应用

其他 2020-03-30 13:18:18 阅读次数: 0

一、配置SQLAlchemy

1.安装包

pip install flask-sqlalchemy
pip install pymysql

2.配置数据库

a)配置SQLALCHEMY_DATABASE_URI SQLALCHEMY_TRACK_MODIFICATIONS

>>>root 用户名
>>>password 密码
>>>localhost 数据库地址：本地数据库 / 服务器地址

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:passowrd@localhost:3306/数据库名称'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
b)初始化
SQLAlchemy(app=app)

二、model模型

1.数据类型

a)String(长度) 字符串
b)Integer 整数
c)Date 时间

2.参数

a)primary_key 主键
b)autoincrement 从1开始，每次自动增加1
c)unique 唯一
d)default 默认
e)nullable 是否允许为空值

3.创建模型

a)知识点：

>>>db = SQLAlchemy() 实例化
>>>db.Model 继承model类
>>>db.Column() 插入属性
>>>db.String(20) 数据类型
>>>__tablename__ 指定表名称
>>>def __init__(self, 参数1, 参数2) 模型初始化
初始化的作用：在创建实例时非常方便，如创建一个姓名为王小，年龄20的学生，可以直接写作：Student('王小', 20)

b)实例

创建一个学生模型，保存学生姓名、年龄信息。

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class Student(db.Model):

s_id <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>Integer<span class="token punctuation">,</span> primary_key<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">,</span> autoincrement<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
s_name <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>String<span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">,</span> unique<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
s_age <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>Integer<span class="token punctuation">,</span> default<span class="token operator">=</span><span class="token number">18</span><span class="token punctuation">)</span>

__tablename__ <span class="token operator">=</span> <span class="token string">'student'</span>


<span class="token keyword">def</span> <span class="token function">__init__</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> name<span class="token punctuation">,</span> age<span class="token punctuation">)</span><span class="token punctuation">:</span>
    self<span class="token punctuation">.</span>s_name <span class="token operator">=</span> name
    self<span class="token punctuation">.</span>s_age <span class="token operator">=</span> age

创建一个班级模型，保存班级名称、班级描述、班级创建时间信息。

class Grade(db.Model):

g_id <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>Integer<span class="token punctuation">,</span> primary_key<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">,</span> autoincrement<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
g_name <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>String<span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span><span class="token punctuation">,</span> unique<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
g_desc <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>String<span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span><span class="token punctuation">,</span>nullable<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
g_time <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>Date<span class="token punctuation">,</span> default<span class="token operator">=</span>datetime<span class="token punctuation">.</span>now<span class="token punctuation">)</span>

__tablename__ <span class="token operator">=</span> <span class="token string">'grade'</span>

<span class="token keyword">def</span> <span class="token function">__init__</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> name<span class="token punctuation">,</span> desc<span class="token punctuation">)</span><span class="token punctuation">:</span>
    self<span class="token punctuation">.</span>g_name <span class="token operator">=</span> name
    self<span class="token punctuation">.</span>s_desc <span class="token operator">=</span> desc

>>>注意：Flask中创建的模型，不会自动创建id字段，需要自己定义。

4.一对多关系

通过如下实例阐述flask中一对多关系。
实例：给上述的学生表添加一个s_grade外键，链接到班级表，指定每个学生所在的班级。

a)学生表中添加s_grade字段：

>>>必须先指定s_grade的数据类型db.Integer，再指定外键信息db.ForeignKey。
>>>db.ForeignKey(‘参数’)
参数grade.g_id含义：grade是被关联表中__tablename__ 指定的表名称，g_id是被关联表的主键名。

s_grade = db.Column(db.Integer, db.ForeignKey('grade.g_id'), nullable=True)
b)班级表中添加students字段：

在django中设置外键时只需要在要设置外键的表中添加外键，而不需要在被关联表中进行任何操作。但是在SQLAlchemy建模中，还需要在被关联的模型中添加关系。这里在Grade模型中新建了一个名叫students的属性用来表示当前班级中包含的学生列表。
格式：db.relationship(‘参数1’, backref='参数2', lazy=True)

students = db.relationship('Student', backref='stu', lazy=True)

如上所示，students被定义成一个db.relationship对象，该对象的构造函数由两部分组成:
>>>第一部分： 'Student'表示关系的另一端模型的名称.
>>>第二部分： 是一个名叫backref的参数，叫做反向关系，我们将其设置成'stu'，它会像Student模型中添加一个名叫做stu的属性，这个属性可以替代s_grade访问Grade模型,但是它获取的是Grade模型的对象,而非Grade模型对应的g_id的值。

c)一对多的应用

实例1：通过学生id查询学生的信息，和该学生所在班级的信息
>>>a)视图

@grade.route('/selectgradebystu/<int:stuid>/')
def select_grade_by_stu(stuid):

stu <span class="token operator">=</span> <span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>get<span class="token punctuation">(</span>stuid<span class="token punctuation">)</span>
grade <span class="token operator">=</span> stu<span class="token punctuation">.</span>stu

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'student_grade.html'</span><span class="token punctuation">,</span> stu<span class="token operator">=</span>stu<span class="token punctuation">,</span> grade<span class="token operator">=</span>grade<span class="token punctuation">)</span>

>>>b)html页面解析


{% extends 'base_main.html' %}

{% block title %}
根据学生查询班级
{% endblock %}

{% block content %}
学生编号：{{ stu.s_id }}
学生姓名：{{ stu.s_name }}
学习年龄：{{ stu.s_age }}
班级名称：{{ grade.g_name }}
{% endblock %}

>>>c)演示结果


>>>d)比对数据库


image.png

实例2：通过班级id查找班级所有学生信息
>>>a)视图

@grade.route('/selectstubygrade/<int:gradeid>/')
def select_stu_by_grade(gradeid):

grade <span class="token operator">=</span> <span class="token constant">Grade</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>get<span class="token punctuation">(</span>gradeid<span class="token punctuation">)</span>
stus <span class="token operator">=</span> grade<span class="token punctuation">.</span>students

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'grade_student.html'</span><span class="token punctuation">,</span> grade<span class="token operator">=</span>grade<span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">)</span>

>>>b)html页面解析


{% extends 'base_main.html' %}

{% block title %}
班级找学生
{% endblock %}

{% block content %}
班级编号：{{ grade.g_id }}
<ul>
{% for stu in stus %}
<li>
学生编号：{{ stu.s_id }}
学生姓名：{{ stu.s_name }}
学生年龄：{{ stu.s_age }}
</li>
{% endfor %}

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>ul</span><span class="token punctuation">&gt;</span></span>

{% endblock %}

>>>c)演示结果


>>>d)比对数据库


知识点：

1.想通过外键所在表查询被关联表的信息，不使用外键，而是使用backref指定的名称。


2.想通过被关联表查询外键所在表信息，使用被关联表中添加的字段名称即可。


5.多对多关系

多对多关系：假设存在一个学生表，和一个课程表，一个学生可以选择多门课程，一门课程可以被多个学生选择，那么学生和课程之间就是多对多的关系。
>>>学生表

class Student(db.Model):

s_id <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>Integer<span class="token punctuation">,</span> primary_key<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">,</span> autoincrement<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
s_name <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>String<span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">,</span> unique<span class="token operator">=</span><span class="token boolean">True</span><span class="token punctuation">)</span>
s_age <span class="token operator">=</span> db<span class="token punctuation">.</span>Column<span class="token punctuation">(</span>db<span class="token punctuation">.</span>Integer<span class="token punctuation">,</span> default<span class="token operator">=</span><span class="token number">18</span><span class="token punctuation">)</span>

__tablename__ <span class="token operator">=</span> <span class="token string">'student'</span>

<span class="token keyword">def</span> <span class="token function">__init__</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> name<span class="token punctuation">,</span> age<span class="token punctuation">)</span><span class="token punctuation">:</span>
    self<span class="token punctuation">.</span>s_name <span class="token operator">=</span> name
    self<span class="token punctuation">.</span>s_age <span class="token operator">=</span> age

>>>课程表

class Course(db.Model):
    c_id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    c_name = db.Column(db.String(10), unique=True)

__tablename__ <span class="token operator">=</span> <span class="token string">'course'</span>

<span class="token keyword">def</span> <span class="token function">__init__</span><span class="token punctuation">(</span>self<span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">:</span>
    self<span class="token punctuation">.</span>c_name <span class="token operator">=</span> name

flask中多对多关系仍使用定义一对多关系的 db.relationship() 方法进行定义，但在多对多关系中，增加了 secondary 参数，用于指定关联表。此处的关联表是需要单独创建的一个表，不是模型，SQLAlchemy 会自动接管这个表。多对多关系可以在关联的两个类中的任何一个类中定义， backref 参数会处理好关系的另一侧。

a)创建关联表

格式：db.Table('参数1‘, db.Column('参数2', db.参数3, db.ForeignKey('参数4')))
>>>参数1：关联表的名称
>>>参数2：字段名称
>>>参数3：数据类型
>>>参数4：外键名称，格式和一对多中格式相同

sc = db.Table('sc',
              db.Column('s_id', db.Integer, db.ForeignKey('student.s_id'), primary_key=True),
              db.Column('c_id', db.Integer, db.ForeignKey('course.c_id'), primary_key=True)
              )

b)在任意一个类中添加字段：

格式：db.relationship('参数1', secondary=参数2, backref='参数3')
>>>参数1：关联的另一个类名称
>>>参数2：关联表的表名称
>>>参数3：想要用另一个类调用这个类的信息时，就需要使用此参数，参数名称可自行定义。
如下在课程表中添加students字段，相当于给课程表添加了students属性，通过这个属性可以获取学生的信息，并且学生可以通过cou属性获取课程信息。

students = db.relationship('Student', secondary=sc, backref='cou')

c)多对多的应用

实例1：添加学生选课信息，一次只添加一门课程

>>>a)视图

@stu.route('/stucou/', methods=['GET', 'POST'])
def stu_cou():

<span class="token keyword">if</span> request<span class="token punctuation">.</span>method <span class="token operator">==</span> <span class="token string">'GET'</span><span class="token operator">:</span>
    stus <span class="token operator">=</span> Student<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">all</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
    cous <span class="token operator">=</span> Course<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">all</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
    <span class="token keyword">return</span> <span class="token function">render_template</span><span class="token punctuation">(</span><span class="token string">'stu_cou.html'</span><span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">,</span> cous<span class="token operator">=</span>cous<span class="token punctuation">)</span>
<span class="token keyword">else</span><span class="token operator">:</span>
    s_id <span class="token operator">=</span> request<span class="token punctuation">.</span>form<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">'student'</span><span class="token punctuation">)</span>
    c_id <span class="token operator">=</span> request<span class="token punctuation">.</span>form<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">'course'</span><span class="token punctuation">)</span>

    stu <span class="token operator">=</span> Student<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span>s_id<span class="token punctuation">)</span>
    cou <span class="token operator">=</span> Course<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span>c_id<span class="token punctuation">)</span>

    cou<span class="token punctuation">.</span>students<span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span>stu<span class="token punctuation">)</span>
    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>cou<span class="token punctuation">)</span>
    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span>

    <span class="token keyword">return</span> <span class="token string">'学生选课成功'</span>

>>>b)html页面解析


{% extends 'base_main.html' %}

{% block title %}
学生课程信息
{% endblock %}

{% block extCSS %}
<link rel=“stylesheet” href="{{ url_for(‘static’, filename=‘css/h3.css’) }}">
{% endblock %}

{% block content %}
<form action="" method=“post”>

    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>h3</span><span class="token punctuation">&gt;</span></span>学生1信息：<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>h3</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>select</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>student<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>
        <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>请选择学生信息<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% for stu in stus %}
            <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>{{ stu.s_id }}<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>{{ stu.s_name }}<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% endfor %}
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>select</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>h3</span><span class="token punctuation">&gt;</span></span>课程信息:<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>h3</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>select</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>course<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>
        <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>请选择课程信息<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% for cou in cous %}
            <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>{{ cou.c_id }}<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>{{ cou.c_name }}<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% endfor %}
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>select</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>input</span> <span class="token attr-name">type</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>submit<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>提交<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>form</span><span class="token punctuation">&gt;</span></span>

{% endblock %}

>>>c)演示结果


>>>d)比对数据库
点击提交，会在数据库sc表中创建一条记录


实例2：添加学生选课信息，一次添加多门课程

>>>a)视图

@stu.route('/stucou/', methods=['GET', 'POST'])
def stu_cou():

<span class="token keyword">if</span> request<span class="token punctuation">.</span>method <span class="token operator">==</span> <span class="token string">'GET'</span><span class="token operator">:</span>
    stus <span class="token operator">=</span> Student<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">all</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
    cous <span class="token operator">=</span> Course<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">all</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
    <span class="token keyword">return</span> <span class="token function">render_template</span><span class="token punctuation">(</span><span class="token string">'stu_cou.html'</span><span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">,</span> cous<span class="token operator">=</span>cous<span class="token punctuation">)</span>
<span class="token keyword">else</span><span class="token operator">:</span>
    s_id <span class="token operator">=</span> request<span class="token punctuation">.</span>form<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">'student'</span><span class="token punctuation">)</span>
    c_ids <span class="token operator">=</span> request<span class="token punctuation">.</span>form<span class="token punctuation">.</span><span class="token function">getlist</span><span class="token punctuation">(</span><span class="token string">'course'</span><span class="token punctuation">)</span>

    stu <span class="token operator">=</span> Student<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span>s_id<span class="token punctuation">)</span>
    <span class="token keyword">for</span> c_id <span class="token keyword">in</span> c_ids<span class="token operator">:</span>
        cou <span class="token operator">=</span> Course<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span>c_id<span class="token punctuation">)</span>
        cou<span class="token punctuation">.</span>students<span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span>stu<span class="token punctuation">)</span>
        db<span class="token punctuation">.</span>session<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>cou<span class="token punctuation">)</span>
        db<span class="token punctuation">.</span>session<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span>

    <span class="token keyword">return</span> <span class="token string">'学生选课成功'</span>

>>>html页面解析


{% extends 'base_main.html' %}

{% block title %}
学生课程信息
{% endblock %}

{% block extCSS %}
<link rel=“stylesheet” href="{{ url_for(‘static’, filename=‘css/h3.css’) }}">
{% endblock %}

{% block content %}
<form action="" method=“post”>

    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>h3</span><span class="token punctuation">&gt;</span></span>学生1信息：<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>h3</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>select</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>student<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>
        <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>请选择学生信息<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% for stu in stus %}
            <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>{{ stu.s_id }}<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>{{ stu.s_name }}<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% endfor %}
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>select</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>h3</span><span class="token punctuation">&gt;</span></span>课程信息:<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>h3</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>select</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>course<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>
        <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>请选择课程信息<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% for cou in cous %}
            <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>{{ cou.c_id }}<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>{{ cou.c_name }}<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% endfor %}
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>select</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>select</span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>course<span class="token punctuation">"</span></span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>
        <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>请选择课程信息<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% for cou in cous %}
            <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>option</span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>{{ cou.c_id }}<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>{{ cou.c_name }}<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>option</span><span class="token punctuation">&gt;</span></span>
        {% endfor %}
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>select</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>br</span><span class="token punctuation">&gt;</span></span>
    <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>input</span> <span class="token attr-name">type</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>submit<span class="token punctuation">"</span></span> <span class="token attr-name">value</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>提交<span class="token punctuation">"</span></span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>form</span><span class="token punctuation">&gt;</span></span>

{% endblock %}

>>>演示结果


>>>比对数据库


实例3：学生查询选课信息

>>>a)视图

# 查询所有学生信息
@stu.route('/allstu/')
def all_stu():
    stus = Student.query.all()
    return render_template('all_stu.html', stus=stus)

# 查询学生选课信息
@stu.route(’/selectcoubystu/<int:id>/’)
def select_cou_by_stu(id):

stu <span class="token operator">=</span> <span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>get<span class="token punctuation">(</span>id<span class="token punctuation">)</span>
cous <span class="token operator">=</span> stu<span class="token punctuation">.</span>cou

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'stucourse.html'</span><span class="token punctuation">,</span> cous<span class="token operator">=</span>cous<span class="token punctuation">,</span> stu<span class="token operator">=</span>stu<span class="token punctuation">)</span>

>>>b)all_stu.html页面解析

{% extends 'base_main.html' %}

{% block title %}
所有学生信息
{% endblock %}

{% block content %}
<ul>
{% for stu in stus %}
<li>
id:{{ stu.s_id }}
姓名：{{ stu.s_name }}
<a href="/stu/selectcoubystu/{{ stu.s_id }}">所选课程</a>
</li>
{% endfor %}

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>ul</span><span class="token punctuation">&gt;</span></span>

{% endblock %}

>>>c)演示结果：


>>>比对数据库：


实例4：删除学生的某条选课信息

>>>a)视图

@stu.route('/deletecoubyid/<int:s_id>/<int:c_id>/')
def delete_course_by_id(s_id, c_id):

stu <span class="token operator">=</span> Student<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span>s_id<span class="token punctuation">)</span>
cou <span class="token operator">=</span> Course<span class="token punctuation">.</span>query<span class="token punctuation">.</span><span class="token keyword">get</span><span class="token punctuation">(</span>c_id<span class="token punctuation">)</span>

cou<span class="token punctuation">.</span>students<span class="token punctuation">.</span><span class="token keyword">remove</span><span class="token punctuation">(</span>stu<span class="token punctuation">)</span>
db<span class="token punctuation">.</span>session<span class="token punctuation">.</span><span class="token function">commit</span><span class="token punctuation">(</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> <span class="token function">redirect</span><span class="token punctuation">(</span><span class="token function">url_for</span><span class="token punctuation">(</span><span class="token string">'stu.all_stu'</span><span class="token punctuation">)</span><span class="token punctuation">)</span>

>>>b)stucourse.html页面解析


{% extends 'base_main.html' %}

{% block title %}
学生选课信息
{% endblock %}

{% block content %}
{{ stu.s_name }}选课结果：
<ul>
{% for cou in cous %}
<li>
id:{{ cou.c_id }}
课程：{{ cou.c_name }}
<a href="/stu/deletecoubyid/{{ stu.s_id }}/{{ cou.c_id }}/">删除</a>
</li>
{% endfor %}

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>ul</span><span class="token punctuation">&gt;</span></span>

{% endblock %}

>>>c)演示结果


>>>d)对比数据库
点击id=4的对应的删除，数据库中会删除对应数据，如下图，数据库中s_id=1 c_id=4 的记录已经被删除。


三、数据库的操作

1.创建表create_all()

@stu.route('/createtable/')
def create_db():
    db.create_all()
    return '创建成功'

2.删除表drop_all()

a)删除db中所有表

@stu.route('/dropalltable/')
def drop_all_table():
    db.drop_all()
    return '删除成功'

b)删除db中某个表

@stu.route('/droponetable/')
def drop_one_table():
    sql = 'delete table student'
    db.sesion.execute(sql)
    db.session.commit()
    return '删除成功'

3.插入 / 创建实例

>>>注意：最后必须要commit才会真正的在数据库中插入数据，否则数据只会保存在缓存区。为了保证事务的一致性，可以用使用try except捕获异常，如果没有执行commit，就回滚上一步操作。

a)模型未初始化
@stu.route('/createstu/')
def create_stu():

stu <span class="token operator">=</span> Student<span class="token punctuation">(</span><span class="token punctuation">)</span>
stu<span class="token punctuation">.</span>s_name <span class="token operator">=</span> <span class="token string">'lp%d'</span> <span class="token operator">%</span> random<span class="token punctuation">.</span>randrange<span class="token punctuation">(</span><span class="token number">1000</span><span class="token punctuation">)</span>
stu<span class="token punctuation">.</span>s_age <span class="token operator">=</span> <span class="token string">'%d'</span> <span class="token operator">%</span> random<span class="token punctuation">.</span>randrange<span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span>

db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>add<span class="token punctuation">(</span>stu<span class="token punctuation">)</span>
<span class="token keyword">try</span><span class="token punctuation">:</span>
    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>commit<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">except</span><span class="token punctuation">:</span>
    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>rollback<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">return</span> <span class="token string">'创建学生成功'</span>

b)模型初始化
@stu.route('/createstu/')
def create_stu():

stu <span class="token operator">=</span> Student<span class="token punctuation">(</span>random<span class="token punctuation">.</span>randrange<span class="token punctuation">(</span><span class="token number">1000</span><span class="token punctuation">)</span><span class="token punctuation">,</span> random<span class="token punctuation">.</span>randrange<span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">)</span>

db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>add<span class="token punctuation">(</span>stu<span class="token punctuation">)</span>
<span class="token keyword">try</span><span class="token punctuation">:</span>
    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>commit<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">except</span><span class="token punctuation">:</span>
    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>rollback<span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">return</span> <span class="token string">'创建学生成功'</span>

c)插入多条记录 add_all([ ])
def create_stu():

    stu1 <span class="token operator">=</span> Student<span class="token punctuation">(</span>username1<span class="token punctuation">,</span> age1<span class="token punctuation">)</span>
    stu2 <span class="token operator">=</span> Student<span class="token punctuation">(</span>username2<span class="token punctuation">,</span> age2<span class="token punctuation">)</span>
    stu_list <span class="token operator">=</span> <span class="token punctuation">[</span>stu1<span class="token punctuation">,</span> stu2<span class="token punctuation">]</span>

    db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>add_all<span class="token punctuation">(</span>stus<span class="token punctuation">)</span>
    <span class="token keyword">try</span><span class="token punctuation">:</span>
        db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>commit<span class="token punctuation">(</span><span class="token punctuation">)</span>
    <span class="token keyword">except</span><span class="token punctuation">:</span>
        db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>rollback<span class="token punctuation">(</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> <span class="token string">'创建学生成功'</span>

4.查询

a)查询所有数据

>>>方式1：模型.query.all()

用这种方式查询的结果是一个 list 而不是 queryset

@stu.route('/stulist/')
def stu_all():

stus <span class="token operator">=</span> <span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>all<span class="token punctuation">(</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'stulist.html'</span><span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">)</span>

>>>方式2：原生sql语句 session.execute(sql)
@stu.route('/stulist/')
def stu_all():

sql <span class="token operator">=</span> <span class="token string">'select * from student;'</span>
stus <span class="token operator">=</span> db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>execute<span class="token punctuation">(</span>sql<span class="token punctuation">)</span>

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'stulist.html'</span><span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">)</span>

b)筛选数据

>>>方式1：使用sql语句
@stu.route('/studetail/')
def stu_detail():

sql <span class="token operator">=</span> <span class="token string">'select * from student where s_name="cy406" '</span>
stus <span class="token operator">=</span> db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>execute<span class="token punctuation">(</span>sql<span class="token punctuation">)</span>

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'stulist.html'</span><span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">)</span>

>>>方式2：使用 模型.query.属性
(1)filter(模型.字段.运算符 值)
@stu.route('/studetail/')
def stu_detail():

stus <span class="token operator">=</span> <span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>filter<span class="token punctuation">(</span><span class="token constant">Student</span><span class="token punctuation">.</span>s_name <span class="token operator">==</span> <span class="token string">'cy253'</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> render_template<span class="token punctuation">(</span><span class="token string">'stulist.html'</span><span class="token punctuation">,</span> stus<span class="token operator">=</span>stus<span class="token punctuation">)</span>

运算符：

>>>==等于
实例：查询年龄等于18的学生

stus = Student.query.filter(Student.s_age == 18)

>>>__gt__大于
实例：查询年龄大于18的学生

stus = Student.query.filter(Student.s_age.__gt__(18))

>>>__lt__小于
实例：查询年龄小于18的学生

stus = Student.query.filter(Student.s_age.__lt__(18))

>>>__ge__大于等于
实例：查询年龄大于等于18的学生

stus = Student.query.filter(Student.s_age.__ge__(18))

>>>__le__小于等于
实例：查询年龄小于等于18的学生

stus = Student.query.filter(Student.s_age.__le__(18))

>>>in_([值, 值, 值]) 包含在某些值中
实例：查询年龄在16, 18, 20, 23 中的学生

stus = Student.query.filter(Student.s_age.in_([16, 18, 20, 23]))
(2)filter_by(字段 运算符 值)
stus = Student.query.filter_by(s_name='cy716')
(3)order_by('字段')

order_by默认升序，降序排列在字段前面加减号，如下：order_by('-字段')。
实例：按照年龄降序展示所有学生信息

stus = Student.query.order_by('-s_age')
(4)limit(显示条数)

实例：显示年龄最大的三个学生

stus = Student.query.order_by('-s_age').limit(3)
(5)offset(number) 跳过几条数据

实例：跳过前3条记录，显示2条记录，即显示第4条和第5条记录

stus = Student.query.order_by('-s_age').offset(3).limit(2)
(6)get(值)

flask中，get获取的是一个列表，如果每页获取到内容，get返回一个空列表，get中的参数对应主键字段。
实例：获取id为3的学生

stus = Student.query.get(3)
(7)and_ 并且

实例：查询 id 大于5 且 年龄为18 的学生

stus = Student.query.filter(and_(Student.s_age == 18, Student.s_id>5))
(8)or_ 或

实例：查询年龄大于18 或者 名字为 王小的学生

stus = Student.query.filter(or_(Student.s_age > 18, Student.s_name == '王小'))
(9)not_ 非

not_只能加一个限制条件
实例：查询年龄不是18的学生

stus = Student.query.filter(not_(Student.s_age == 18))

5.删除实例

@stu.route('/deletestu/')
def delete_stu():

stu <span class="token operator">=</span> <span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>filter_by<span class="token punctuation">(</span>s_id<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">.</span>first<span class="token punctuation">(</span><span class="token punctuation">)</span>
db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>delete<span class="token punctuation">(</span>stu<span class="token punctuation">)</span>
db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>commit<span class="token punctuation">(</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> redirect<span class="token punctuation">(</span>url_for<span class="token punctuation">(</span><span class="token string">'stu.stu_all'</span><span class="token punctuation">)</span><span class="token punctuation">)</span>

6.更新/修改实例

>>>方式1：

@stu.route('/updatestu/')
def update_stu():

stu <span class="token operator">=</span> <span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>filter_by<span class="token punctuation">(</span>s_id<span class="token operator">=</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">.</span>first<span class="token punctuation">(</span><span class="token punctuation">)</span>
stu<span class="token punctuation">.</span>s_name <span class="token operator">=</span> <span class="token string">'王小二'</span>
db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>commit<span class="token punctuation">(</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> redirect<span class="token punctuation">(</span>url_for<span class="token punctuation">(</span><span class="token string">'stu.stu_all'</span><span class="token punctuation">)</span><span class="token punctuation">)</span>

>>>方式2：update

@stu.route('/updatestu/')
def update_stu():

<span class="token constant">Student</span><span class="token punctuation">.</span>query<span class="token punctuation">.</span>filter<span class="token punctuation">(</span><span class="token constant">Student</span><span class="token punctuation">.</span>s_id <span class="token operator">==</span> <span class="token string">'1'</span><span class="token punctuation">)</span><span class="token punctuation">.</span>update<span class="token punctuation">(</span><span class="token punctuation">{</span><span class="token string">'s_name'</span><span class="token punctuation">:</span> <span class="token string">'王大锤'</span><span class="token punctuation">}</span><span class="token punctuation">)</span>
db<span class="token punctuation">.</span>session<span class="token punctuation">.</span>commit<span class="token punctuation">(</span><span class="token punctuation">)</span>

<span class="token keyword">return</span> redirect<span class="token punctuation">(</span>url_for<span class="token punctuation">(</span><span class="token string">'stu.stu_all'</span><span class="token punctuation">)</span><span class="token punctuation">)</span>

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