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HomeBackend DevelopmentPython Tutorial在Python的Flask框架下使用sqlalchemy库的简单教程

flask中的sqlalchemy 相比于sqlalchemy封装的更加彻底一些 , 在一些方法上更简单

首先import类库:

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">from flask import Flask 
  from flask.ext.sqlalchemy import SQLAlchemy</span>

 


然后,需要加载 数据库路径

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">mysqlname='<span style="color: rgb(230, 219, 116); font-family: 'Source Code Pro'; font-size: 13pt; background-color: rgb(39, 40, 34);">mysql://user:passwd@127.0.0.1/student&#63;charset=utf8</span>'</span> 

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">app = Flask(__name__) 
  app.config['SQLALCHEMY_DATABASE_URI'] = mysqlname 
  db = SQLAlchemy(app)</span> 


通过前面两步 ,我们已经让flask和数据库联系到了一起

下面我们要把 flask和具体的表联系在一起、

这样建立一个model模型

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">class User(db.Model): 
   
    """存储 每种报警类型的数量 , 以 分钟 为单位进行统计 
    :param source: string ,报警来源 
    :param network_logic_area: string ,该报警所属的逻辑网络区域 
    :param start_time: datetime , 报警发生时间 
    """ 
   
    __tablename__ = 'hello' 
    id = db.Column(db.Integer , primary_key = True) 
    source = db.Column(db.String(255) ) 
    network_logic_area = db.Column(db.String(255) ) 
    start_time = db.Column(db.DateTime) 
    count = db.Column(db.Integer) 
   
    def __init__(self , source , network_logic_area , start_time , count): 
      self.source = source 
      self.network_logic_area = network_logic_area 
      self.start_time = start_time 
      self.count = count 
   
    def alter(self): 
      self.count += 1;</span> 

上面这个代码,就让falsk和具体的表hello联系在了一起

在这个类中 ,我们首先要指定表,然后把这个表中的列都列出来,最后定义一个 初始化函数 , 让后面插入数据使用


现在开始具体的数据库操作:

1、insert

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">    p = User(........) 
      db.session.add(p) 
      db.session.commit()</span> 

通过 类User构造了一条数据

2、find

用主键获取数据:
Code example:

User.query.get(1)

<User
 u'admin'>

通过一个精确参数进行反查:
Code example:

peter
=

User.query.filter_by(username='peter').first() 
#注意:精确查询函数query.filter_by(),是通过传递参数进行查询;其他增强型查询函数是query.filter(),通过传递表达式进行查询。

print(peter.id) 
#如果数据不存在则返回None

模糊查询:
Code example:
 

User.query.filter(User.email.endswith('@example.com')).all()

[<User
 u'admin'>,
 <User u'guest'>]

逻辑非1:
Code example:
 

peter
=

User.query.filter(User.username
 !=

'peter').first()

print(peter.id)

逻辑非2:
Code example:
 

from

sqlalchemy import

not_

peter
=

User.query.filter(not_(User.username=='peter')).first()

print(peter.id)

逻辑与:
Code example:

from

sqlalchemy import

and_

peter
=

User.query.filter(and_(User.username=='peter',
 User.email.endswith('@example.com'))).first()

print(peter.id)

逻辑或:
Code example:

from

sqlalchemy import

or_

peter
=

User.query.filter(or_(User.username
 !=

'peter',
 User.email.endswith('@example.com'))).first()

print(peter.id)

filter_by:这个里面只能放具体放入条件,不能放一个复杂的计算 ,

filter: 这个里面可以放一些复杂的计算

.first:取第一条数据

.all:取出所有数据

还有一个其他的方法,可以进行排序、计数之类的操作

3、使用sql语句

可以通过 前面构造的 db 直接使用sql的原生语句

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">insert_table.db.engine.execute(' ..... ')</span> 


4、delete

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">me = User(........)</span> 

在CODE上查看代码片派生到我的代码片

  <span style="font-size:18px;">db.session.delete(me) 
  db.session.commit()</span> 

5、更新数据

Code example:
 
u
=

User.query.first()

u.username
=

'guest' 
#更新数据和变量赋值那么简单,但必须是通过查询返回的对象。

db.session.commit()

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