FlaskSQLAlchemy

SQLAlchemy是一个基于Python实现的ORM框架。该框架建立在 DB API之上，使用关系对象映射进行数据库操作，简言之便是：将类和对象转换成SQL，然后使用数据API执行SQL并获取执行结果。

pip3 install sqlalchemy

 

组成部分：

• Engine，框架的引擎
• Connection Pooling ，数据库连接池
• Dialect，选择连接数据库的DB API种类
• Schema/Types，架构和类型
• SQL Exprression Language，SQL表达式语言

SQLAlchemy本身无法操作数据库，其必须以来pymsql等第三方插件，Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作，如：

MySQL-Python
    mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>
    
pymysql
    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
    
MySQL-Connector
    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
    
cx_Oracle
    oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]
    
更多：http://docs.sqlalchemy.org/en/latest/dialects/index.html

 1. 执行原生SQL语句

import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine
 
engine = create_engine(
    "mysql+pymysql://root:123@127.0.0.1:3306/t1?charset=utf8",
    max_overflow=0,  # 超过连接池大小外最多创建的连接
    pool_size=5,  # 连接池大小
    pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错
    pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）
)
 
 
def task(arg):
    conn = engine.raw_connection()
    cursor = conn.cursor()
    cursor.execute(
        "select * from t1"
    )
    result = cursor.fetchall()
    cursor.close()
    conn.close()
 
 
for i in range(20):
    t = threading.Thread(target=task, args=(i,))
    t.start()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5)


def task(arg):
    conn = engine.contextual_connect()
    with conn:
        cur = conn.execute(
            "select * from t1"
        )
        result = cur.fetchall()
        print(result)


for i in range(20):
    t = threading.Thread(target=task, args=(i,))
    t.start()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine
from sqlalchemy.engine.result import ResultProxy
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5)


def task(arg):
    cur = engine.execute("select * from t1")
    result = cur.fetchall()
    cur.close()
    print(result)


for i in range(20):
    t = threading.Thread(target=task, args=(i,))
    t.start()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from db import Users

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)


def task(arg):
    session = Session()

    obj1 = Users(name="alex1")
    session.add(obj1)

    session.commit()


for i in range(10):
    t = threading.Thread(target=task, args=(i,))
    t.start()

多线程执行示例

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from db import Users

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)


def task(arg):
    session = Session()

    obj1 = Users(name="alex1")
    session.add(obj1)

    session.commit()


for i in range(10):
    t = threading.Thread(target=task, args=(i,))
    t.start()

多线程执行示例

增

#新增一条数据
#原生sql：insert  into mysql.hello_word(name,password) values("test2","1234")；
obj = User(name="test", password="1234")  #生成你要创建的数据对象
session.add(obj) #把要创建的数据对象添加到这个session里， 一会统一创建
session.commit() #统一提交，创建数据，在此之前数据库是不会有新增数据的
 
#新增多条数据
#原生sql:insert  into mysql.hello_word(name,password) values("test2","1234"),("test3","123");
obj = User(name="test", password="1234")
obj1 = User(name="test", password="1234")
session.add_all([obj,obj1])
session.commit()<br><br>#回滚，在session.add()之后，在session.commit()之前，想把添加至session缓存中的数据清除，使用rollback()函数回滚即可<br>Session.rollback()

删

#原生sql:mysql.hello_word where id > 5;
session.query(User).filter(User.id > 5).delete() #通过session查询User类，然后过滤出id>5的进行删除
session.commit() #提交

改

#①第一种方式
data = Session.query(User).filter_by(name="test1").first()  #获取数据
data.name = "test"  #修改数据
Session.commit()   #提交
 
#②第二种方式，通过查找表，过滤条件，然后更新对应参数
session.query(User).filter(User.id > 15).update({"name": "test"})
session.query(User).filter(User.id == 18).update({User.name: "hello"}, synchronize_session=False)
session.query(User).filter_by(name="test1").update({User.password: User.name}, synchronize_session="evaluate")
session.commit()
 
#③synchronize_session解释，用于query在进行delete or update操作时，对session的同步策略：
#1、synchronize_session=False，不对session进行同步，直接进行delete or update操作。
#2、synchronize_session="evaluate"，在delete or update操作之前，用query中的条件直接对session的identity_map中的objects进行eval操作，将符合条件的记录下来，　在delete or update操作之后，将符合条件的记录删除或更新。

查

#原生sql:select * from mysql.hello_word;
ret = session.query(User).all()  #查询所有
#也可以这样写：
ret = Session.query(User.name,User.id).all()
 
#原生slq:select name,password from mysql.hello_word;
ret = session.query(User.name, User.extra).all()  #只查询name和extra字段所以所有数据
 
#原生sql:select * from mysql.hello_word where name="test1";
ret = session.query(User).filter_by(name='test1').all() #查询name='alex'的所有数据
ret = session.query(User).filter_by(name='test1').first()#查询name='alex'的第一条数据
 
#查询id>5的name字段内容，且以id大小排序
#原生sql；select name from mysql.hello_word where id >5 order by id；
ret = session.query(User).filter(text("id>:value and name=:name")).params(value=5, name='test2').order_by(User.id).all()
 
#根据原生sql查询数据
ret = session.query(User).from_statement(text("SELECT * FROM hello_word where name=:name")).params(name='test1').all()

 filter和filter_by使用的区别

#filter用于sql表达式查询过滤，如>，<, ==,等表达式
session.query(MyClass).filter(MyClass.name == 'some name')
#filter_by用于关键字查询过滤，如id=value,name=value
session.query(MyClass).filter_by(name = 'some name')

重构__repr__方法，将5.1 中ret内存对象按__repr__方法中定义的格式进行打印显示

class User(Base):
    __tablename__ = "hello_word"  # 表名
    id = Column(Integer, primary_key=True)
    name = Column(String(32))
    password = Column(String(64))
 
    def __repr__(self):    # 使返回的内存对象变的可读
        return "<id:{0} name:{1} password:{2}>".format(self.id, self.name, self.password)
 
#Base.metadata.create_all(connect)  # 创建标结构
 
session_class = sessionmaker(bind=connect)  # 创建与数据库的会话session class ,这里返回给session的是个class,不是实例
session = session_class()   # 生成session实例
 
user = session.query(User).all()  #查询全部
print(user)
 
#输出
[<id:1 name:test1 password:1234>, <id:2 name:test1 password:1234>, <id:8 name:test2 password:1234>, <id:9 name:test3 password:123>, <id:10 name:test4 password:123>, <id:11 name:test5 password:123>, <id:12 name:test2 password:1234>, <id:13 name:test3 password:123>, <id:14 name:test4 password:123>, <id:15 name:test5 password:123>, <id:16 name:test2 password:1234>, <id:17 name:test3 password:123>, <id:18 name:test4 password:123>, <id:19 name:test5 password:123>]

 其他操作

#多条件查询
#原生sql:select * from mysql.hello_word where id >2 and id < 19
data = session.query(User).filter(Use.id>2).filter(Use.id<19).all()
 
#通配符

#原生sql:select * from mysql.hello_word where name like "test%" #"test_"、%test%
data = session.query(User).filter(User.name.like('test%')).all() #匹配以test开头，而后跟多个字符
data = session.query(User).filter(User.name.like('test_')).all() #匹配以test开头，而后跟一个字符
data = session.query(User).filter(~User.name.like('e%')).all() #加~后，忽略like(),直接匹配所有
#原生sql select count(name) from mysql.hello_word where name like "%test%"
data = session.query(User).filter(User.name.like("%qigao%")).count() # 模糊匹配并计数

#分组

from sqlalchemy import func #导入func 进行函数操作
#原生sql:select count(name),name from mysql.hello_word group by name
data =session.query(func.count(User.name),User.name).group_by(User.name).all()  #根据User.name分组
#原生sql:select max(id),sum(id),min(id) from mysql.hello_word group by name  #根据name 分组
data =session.query(func.max(User.id),func.sum(User.id),func.min(User.id)).group_by(User.name).all()
#原生sql:select max(id),sum(id),min(id) from mysql.hello_word group by name having min(id > 2) # 根据name分组且id>2
data = session.query(func.max(User.id),func.sum(User.id),func.min(User.id)).group_by(User.name).having(func.min(User.id) >2).all()

#排序

#原生sql:select * from mysql.hello_word  order by id asc
data = session.query(User).order_by(User.id.asc()).all() #将所有数据根据 “列” 从小到大排列
#原生sql:select * from mysql.hello_word  order by id desc, id asc
data = session.query(User).order_by(User.id.desc(), User.id.asc()).all()#将所有数据根据 “列1” 从大到小排列,如果相同则按照“列2”由小到大排列
 
 
#条件表达式 in、between、 and 、or
data = session.query(User).filter_by(name='test').all()
data = session.query(User).filter(User.id > 1, Users.name == 'test').all()
data = session.query(User).filter(User.id.between(1, 3), Users.name == 'test').all()
data = session.query(User).filter(User.id.in_([1,3,4])).all()
data = session.query(User).filter(~User.id.in_([1,3,4])).all()
data = session.query(User).filter(Users.id.in_(session.query(User.id).filter_by(name='test'))).all()
 
from sqlalchemy import and_, or_
data = session.query(User).filter(and_(User.id > 3, Users.name == 'test')).all()
data = session.query(User).filter(or_(User.id < 2, Users.name == 'test')).all()
data = session.query(User).filter(or_(User.id < 2,and_(User.name == 'test',User.id > 3),User.password != "")).all()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text
from sqlalchemy.engine.result import ResultProxy
from db import Users, Hosts, Hobby, Person

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()
# 添加
"""
session.add_all([
    Hobby(caption='乒乓球'),
    Hobby(caption='羽毛球'),
    Person(name='张三', hobby_id=3),
    Person(name='李四', hobby_id=4),
])

person = Person(name='张九', hobby=Hobby(caption='姑娘'))
session.add(person)

hb = Hobby(caption='人妖')
hb.pers = [Person(name='文飞'), Person(name='博雅')]
session.add(hb)

session.commit()
"""

# 使用relationship正向查询
"""
v = session.query(Person).first()
print(v.name)
print(v.hobby.caption)
"""

# 使用relationship反向查询
"""
v = session.query(Hobby).first()
print(v.caption)
print(v.pers)
"""

session.close()

基于relationship操作ForeignKey

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
from sqlalchemy.sql import text
from sqlalchemy.engine.result import ResultProxy
from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()
# 添加
"""
session.add_all([
    Server(hostname='c1.com'),
    Server(hostname='c2.com'),
    Group(name='A组'),
    Group(name='B组'),
])
session.commit()

s2g = Server2Group(server_id=1, group_id=1)
session.add(s2g)
session.commit()


gp = Group(name='C组')
gp.servers = [Server(hostname='c3.com'),Server(hostname='c4.com')]
session.add(gp)
session.commit()


ser = Server(hostname='c6.com')
ser.groups = [Group(name='F组'),Group(name='G组')]
session.add(ser)
session.commit()
"""


# 使用relationship正向查询
"""
v = session.query(Group).first()
print(v.name)
print(v.servers)
"""

# 使用relationship反向查询
"""
v = session.query(Server).first()
print(v.hostname)
print(v.groups)
"""


session.close()

基于relationship操作m2m