标签：多对多 不可 nec connect sel 分页 rgs add iter
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。
SQLAlchemy安装
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
修改表：在数据库添加字段，类对应上
1执行原生sql（不常用）
import time import threading import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.engine.base import Engine engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/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() 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()
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 Base = declarative_base() 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) #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 ) def init_db(): """ 根据类创建数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/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） ) Base.metadata.create_all(engine) def drop_db(): """ 根据类删除数据库表 :return: """ engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/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） ) Base.metadata.drop_all(engine) if __name__ == ‘__main__‘: # drop_db() init_db()
app.py
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from models import Users #"mysql+pymysql://root@127.0.0.1:3306/aaa" engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/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="lqz") 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()
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‘)
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‘)
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from models import Users engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/aaa", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) # 每次执行数据库操作时，都需要创建一个session session = Session() # ############# 执行ORM操作 ############# obj1 = Users(name="lqz") session.add(obj1) # 提交事务 session.commit() # 关闭session session.close()
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:123@127.0.0.1:3306/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()
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:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # ################ 添加 ################ """ obj1 = Users(name="wupeiqi") session.add(obj1) session.add_all([ Users(name="lqz"), Users(name="egon"), Hosts(name="c1.com"), ]) 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" : "lqz"}) #类似于django的F查询 session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) 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 == "lqz").all() r4 = session.query(Users).filter_by(name=‘lqz‘).all() r5 = session.query(Users).filter_by(name=‘lqz‘).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()
# 条件 ret = session.query(Users).filter_by(name=‘lqz‘).all() #表达式，and条件连接 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() #注意下划线 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all() #~非，除。。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） 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 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() #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() #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 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（了解）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()
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 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 查询 # cursor = session.execute(‘select * from users‘) # result = cursor.fetchall() # 添加 cursor = session.execute(‘insert into users(name) values(:value)‘,params={"value":‘lqz‘}) session.commit() print(cursor.lastrowid) session.close()
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) #添加二 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) """ #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()
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()
标签：多对多 不可 nec connect sel 分页 rgs add iter
原文地址：https://www.cnblogs.com/linche/p/12681805.html
