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：
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<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
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<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?charset=utf8</span>'</span>
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<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
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<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
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<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
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<span style="font-size:18px;">insert_table.db.engine.execute(' ..... ')</span>
4、delete
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<span style="font-size:18px;">me = User(........)</span>
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<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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