目录
3-2 多对多关系 - relationship 内 secondary参数 +第三张表
四、基于scoped_session实现线程安全 - sessionmaker
7-1-2 手动链表形成查询(不急于relationship的查询方式)
一、介绍
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。
1-0 安装
1-1 组成结构
- 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:
''' 支持的第三方模块 ''' pymysql mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>] MySQL-Python mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname> 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
二、简单使用
SQLAlchemy 使用注意
- 无法创建数据库,必须提前手动创建
- 无法修改字段,只能在数据库内将字段修改后,在model类内进行对应操作
- 只能创建表,无法删除表
- 进行增删改,即修改操作时,必须在最后进行commit进行提交处理
2-1 使用 SQLAlchemy 进行原生SQL操作
import time import threading import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.engine.base import Engine engine = create_engine( "mysql+pymysql://root:[email protected]:3306/test?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() # SQL操作 cursor.execute( "select * from app01_book" ) result = cursor.fetchall() print(result) cursor.close() conn.close() for i in range(20): t = threading.Thread(target=task, args=(i,)) t.start() ----------------------------------------------------- # 保证线程安全 Session = sessionmaker(bind=engine) session = Session() # 执行SQL的添加操作 cursor = session.execute('insert into users(name) values(:value)',params={"value":'test'}) session.commit() print(cursor.lastrowid)
2-2 ORM使用
''' models.py ''' import datetime from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index # 同 Django内的model.Mode Base = declarative_base() # 一类对应一表 class Users(Base): __tablename__ = 'users' # 数据库表名称 id = Column(Integer, primary_key=True) # id 主键 name = Column(String(32), index=True, nullable=False) # name列,索引,不可为空 # email = Column(String(32), unique=True) # unique是否唯一 # 注意!!!datetime.datetime.now 不能加括号,加了括号,以后永远是当前时间 # ctime = Column(DateTime, default=datetime.datetime.now) # extra = Column(Text, nullable=True) __table_args__ = ( # UniqueConstraint('id', 'name', name='uix_id_name'), # 联合唯一 # Index('ix_id_name', 'name', 'email'), # 索引 ) class Hobby(Base): __tablename__ = 'hobby' id = Column(Integer, primary_key=True) caption = Column(String(50), default='篮球') class Person(Base): __tablename__ = 'person' nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) # hobby指的是tablename而不是类名, hobby_id = Column(Integer, ForeignKey("hobby.id")) # 跟数据库无关,不会新增字段,只用于快速链表操作 # 类名,backref用于反向查询 # hobby = relationship('Hobby', backref='pers') def init_db(): """ 根据类创建数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:[email protected]:3306/aaa?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) ) # 创建继承base的所有表 Base.metadata.create_all(engine) def drop_db(): """ 根据类删除数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:[email protected]:3306/aaa?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) ) # 将继承base的所有表删除 Base.metadata.drop_all(engine) if __name__ == '__main__': # drop_db() init_db()
''' 视图函数 ''' from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from models import Users # 项目文件内的models内导入存在的表类 # "mysql+pymysql://[email protected]:3306/aaa" engine = create_engine("mysql+pymysql://root:[email protected]:3306/aaa", max_overflow=0, pool_size=5) Connection = sessionmaker(bind=engine) # 每次执行数据库操作时,都需要创建一个Connection con = Connection() # ############# 执行ORM操作 ############# obj1 = Users(name="test") con.add(obj1) # 提交事务 con.commit() # 关闭session,其实是将连接放回连接池 con.close()
三、model内的多表关系 - relationship
3-1 一对多关系 - relationship
class Hobby(Base): __tablename__ = 'hobby' id = Column(Integer, primary_key=True) caption = Column(String(50), default='篮球') class Person(Base): __tablename__ = 'person' nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) # hobby指的是tablename而不是类名 hobby_id = Column(Integer, ForeignKey("hobby.id")) # 跟数据库无关,不会新增字段,只用于快速链表操作 # 类名,backref用于反向查询 hobby=relationship('Hobby',backref='pers')
3-2 多对多关系 - relationship 内 secondary参数 +第三张表
class Boy2Girl(Base): __tablename__ = 'boy2girl' id = Column(Integer, primary_key=True, autoincrement=True) girl_id = Column(Integer, ForeignKey('girl.id')) boy_id = Column(Integer, ForeignKey('boy.id')) class Girl(Base): __tablename__ = 'girl' id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) class Boy(Base): __tablename__ = 'boy' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False) # 与生成表结构无关,仅用于查询方便,放在哪个单表中都可以 servers = relationship('Girl', secondary='boy2girl', backref='boys')
四、基于scoped_session实现线程安全 - sessionmaker
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session from models import Users engine = create_engine("mysql+pymysql://root:[email protected]:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) """ # 线程安全,基于本地线程实现每个线程用同一个session # 特殊的:scoped_session中有原来方法的Session中的一下方法: public_methods = ( '__contains__', '__iter__', 'add', 'add_all', 'begin', 'begin_nested', 'close', 'commit', 'connection', 'delete', 'execute', 'expire', 'expire_all', 'expunge', 'expunge_all', 'flush', 'get_bind', 'is_modified', 'bulk_save_objects', 'bulk_insert_mappings', 'bulk_update_mappings', 'merge', 'query', 'refresh', 'rollback', 'scalar' ) """ #scoped_session类并没有继承Session,但是却又它的所有方法 session = scoped_session(Session) # ############# 执行ORM操作 ############# obj1 = Users(name="alex1") session.add(obj1) # 提交事务 session.commit() # 关闭session session.close()
五、ORM的增删查改
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 db import Users, Hosts engine = create_engine("mysql+pymysql://root:[email protected]:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # ################ 添加 ################ obj1 = Users(name="test") session.add(obj1) session.add_all([ Users(name="name"), Users(name="name2"), Hosts(name="name3"), ]) session.commit() # ################ 删除 ################ session.query(Users).filter(Users.id > 2).delete() session.commit() # ################ 修改 ################ # 传字典 session.query(Users).filter(Users.id > 0).update({"name" : "name"}) # 类似于django的F查询,进行拼接操作 session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) # 四则运算的使用 session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") session.commit() # ################ 查询 ################ r1 = session.query(Users).all() # 只取age列,把name重命名为xx r2 = session.query(Users.name.label('xx'), Users.age).all() # filter传的是表达式,filter_by传的是参数 r3 = session.query(Users).filter(Users.name == "name").all() r4 = session.query(Users).filter_by(name='name').all() r5 = session.query(Users).filter_by(name='name').first() # :value 和:name 相当于占位符,用params传参数 r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all() # 自定义查询sql r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all() # 增,删,改都要commit() session.close()
六、常用操作
# 条件 ret = session.query(Users).filter_by(name='name').all() # 表达式,逗号连接 ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all() ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all() # in_([]) 范围内 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all() # ~非,除指定条件外 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all() # 二次筛选 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all() from sqlalchemy import and_, or_ # or_ 包裹的都是or条件,and_ 包裹的都是and条件 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all() ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all() ret = session.query(Users).filter( or_( Users.id < 2, and_(Users.name == 'eric', Users.id > 3), Users.extra != "" )).all() # 通配符,以e开头,不以e开头 ret = session.query(Users).filter(Users.name.like('e%')).all() ret = session.query(Users).filter(~Users.name.like('e%')).all() # 限制,用于分页,区间 ret = session.query(Users)[1:2] # 排序,根据name降序排列(从大到小) - desc() 降序 ret = session.query(Users).order_by(Users.name.desc()).all() # 第一个条件重复后,再按第二个条件升序排 - asc() 升序 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() '''分组''' from sqlalchemy.sql import func ret = session.query(Users).group_by(Users.extra).all() # 分组之后取最大id,id之和,最小id ret = session.query( func.max(Users.id), func.sum(Users.id), func.min(Users.id)).group_by(Users.name).all() # group之后进行 haviing 筛选 ret = session.query( func.max(Users.id), func.sum(Users.id), func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all() ''' 连表(默认用forinkey关联) ''' ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all() for i in ret: print(i[0].name) # join表,默认是inner join ret = session.query(Person).join(Favor).all() # isouter=True 外连,表示Person left join Favor,没有右连接,反过来即可 ret = session.query(Person).join(Favor, isouter=True).all() # 打印原生sql - 不添加.all() aa=session.query(Person).join(Favor, isouter=True) print(aa) # 自己指定on条件(连表条件),第二个参数,支持on多个条件,用and_,同上 ret = session.query(Person).join(Favor,Person.id==Favor.id, isouter=True).all() # 组合 - UNION 操作符用于合并两个或多个 SELECT 语句的结果集 # union和union all的区别 q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union(q2).all() q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union_all(q2).all()
七、view内对多表关系的操作
7-1 一对多关系
7-1-0 依赖导入 and ORM初始化
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:[email protected]:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session()
7-1-1 添加的两种方式 - add
# 添加方式一 # 手动添加关联关系 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), ]) session.commit() -------------------------------------------------------- # 添加方式二 person = Person(name='张九', hobby=Hobby(caption='姑娘')) session.add(person) session.commit() ------------------------------------------------------------- # 添加方式三,自动进行关联关系操作 hb = Hobby(caption='人妖') hb.pers = [Person(name='文飞'), Person(name='博雅')] session.add(hb) session.commit()
7-1-2 基于relationship的正反向查询
''' model内person表内建立联系 class Person(Base): hobby=relationship('Hobby',backref='pers') ''' # 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)
7-1-2 手动链表形成查询(不急于relationship的查询方式)
# 方式一,自己链表 person_list=session.query(models.Person.name,models.Hobby.caption).join(models.Hobby,isouter=True).all() person_list=session.query(models.Person,models.Hobby).join(models.Hobby,isouter=True).all() for row in person_list: # print(row.name,row.caption) print(row[0].name,row[1].caption) # 方式二:通过relationship person_list=session.query(models.Person).all() for row in person_list: print(row.name,row.hobby.caption) #查询喜欢姑娘的所有人 obj=session.query(models.Hobby).filter(models.Hobby.id==1).first() persons=obj.pers print(persons) session.close()
7-2 多对多关系
7-2-0 依赖导入 and ORM初始化
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:[email protected]:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session()
7-2-1 添加操作
# 添加 # 批量添加 session.add_all([ Server(hostname='c1.com'), Server(hostname='c2.com'), Group(name='A组'), Group(name='B组'), ]) session.commit() # 在第三张表中,添加server表和group表的关系;不对两表内进行新增数据操作 s2g = Server2Group(server_id=1, group_id=1) session.add(s2g) session.commit() # 对Group表进行添加,Group内创建C组,servers表内创建c3.com和c4.com,并建立关系指向C组 gp = Group(name='C组') gp.servers = [Server(hostname='c3.com'),Server(hostname='c4.com')] session.add(gp) session.commit() # 对Server表进行添加,Server内创建c6.com,groups 内创建F/G组,并建立关系指向c6 ser = Server(hostname='c6.com') ser.groups = [Group(name='F组'),Group(name='G组')] session.add(ser) session.commit()
7-2-2 基于relationship的正反向查询
# 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)
八、关联子查询
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, func from sqlalchemy.engine.result import ResultProxy from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group engine = create_engine("mysql+pymysql://root:[email protected]:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 关联子查询:correlate(Group)表示跟Group表做关联,as_scalar相当于对该sql加括号,用于放在后面当子查询 subqry = session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id).correlate(Group).as_scalar() result = session.query(Group.name, subqry) """ SELECT `group`.name AS group_name, (SELECT count(server.id) AS sid FROM server WHERE server.id = `group`.id) AS anon_1 FROM `group` """ ''' select * from tb where id in [select id from xxx]; select id, name, #必须保证此次查询只有一个值 (select max(id) from xxx) as mid from tb 例如,第三个字段只能有一个值 id name mid 1 name1 1,2 不合理 2 name2 2 ''' # 原生SQL """ # 查询 cursor = session.execute('select * from users') result = cursor.fetchall() # 添加 cursor = session.execute('insert into users(name) values(:value)',params={"value":'test'}) session.commit() print(cursor.lastrowid) """ session.close()
九、Flask-SQLAlchemy
db = SQLAlchemy() - 包含配置 - 包含ORM基类 - 包含create_all - engine - 创建连接