SQLAlchemy是一個基於Python實現的ORM框架。該框架創建在 DB API之上,使用關係對象映射進行數據庫操做,簡言之即是:將類和對象轉換成SQL,而後使用數據API執行SQL並獲取執行結果。python
幫助咱們使用類和對象快速實現數據庫操做。mysql
pip3 install sqlalchemy
Engine,框架的引擎sql
Connection Pooling ,數據庫鏈接池數據庫
Dialect,選擇鏈接數據庫的DB API種類session
Schema/Types,架構和類型架構
SQL Exprression Language,SQL表達式語言框架
- 用戶登陸示例
- 用戶註冊示例
- 數據庫獲取數據實時更新(重寫構造方法)ui
#!/usr/bin/env python # -*- coding:utf-8 -*- 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' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) # email = Column(String(32), unique=True) # ctime = Column(DateTime, default=datetime.datetime.now) # extra = Column(Text, nullable=True) __table_args__ = ( # UniqueConstraint('id', 'name', name='uix_id_name'), # Index('ix_id_name', 'name', 'email'), ) def init_db(): """ 根據類建立數據庫表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", #用戶名:密碼@本機ip:數據庫端口3306/數據庫名?字符集 max_overflow=0, # 超過鏈接池大小外最多建立的鏈接 pool_size=5, # 鏈接池大小 pool_timeout=30, # 池中沒有線程最多等待的時間,不然報錯 pool_recycle=-1 # 多久以後對線程池中的線程進行一次鏈接的回收(重置) ) Base.metadata.create_all(engine) def drop_db(): """ 根據類刪除數據庫表 :return: """ engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, # 超過鏈接池大小外最多建立的鏈接 pool_size=5, # 鏈接池大小 pool_timeout=30, # 池中沒有線程最多等待的時間,不然報錯 pool_recycle=-1 # 多久以後對線程池中的線程進行一次鏈接的回收(重置) ) Base.metadata.drop_all(engine) if __name__ == '__main__': drop_db() init_db()
#!/usr/bin/env python # -*- coding:utf-8 -*- 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/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) # 每次執行數據庫操做時,都須要建立一個session session = Session() # ############# 執行ORM操做 ############# obj1 = Users(name="alex1") session.add(obj1) # 提交事務 session.commit() # 關閉session session.close()
#!/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 db import Users, Hosts engine = create_engine("mysql+pymysql://root:123456@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # ################ 添加 ################ """ obj1 = Users(name="yaya") session.add(obj1) session.add_all([ Users(name="yaya"), Users(name="xiaoqiang"), Hosts(name="c1.com"), ]) session.commit() """ # ################ 刪除 ################ """ session.query(Users).filter(Users.id > 2).delete() session.commit() """ # ################ 修改 ################ """ session.query(Users).filter(Users.id > 0).update({"name" : "099"}) 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() """ # ################ 查詢 ################ """ r1 = session.query(Users).all() r2 = session.query(Users.name.label('xx'), Users.age).all() r3 = session.query(Users).filter(Users.name == "yaya").all() r4 = session.query(Users).filter_by(name='alex').all() r5 = session.query(Users).filter_by(name='alex').first() r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all() r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all() """ session.close()
# ############################## 其餘經常使用 ############################### # 1. 指定列 select id,name as cname from users; result = session.query(Users.id,Users.name.label('cname')).all() for item in result: print(item[0],item.id,item.cname) # 2. 默認條件and session.query(Users).filter(Users.id > 1, Users.name == 'eric').all() # 3. between session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all() # 4. in session.query(Users).filter(Users.id.in_([1,3,4])).all() session.query(Users).filter(~Users.id.in_([1,3,4])).all() # 5. 子查詢 session.query(Users).filter(Users.id.in_(session.query(Users.id).filter(Users.name=='eric'))).all() # 6. and 和 or from sqlalchemy import and_, or_ session.query(Users).filter(Users.id > 3, Users.name == 'eric').all() session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all() session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all() session.query(Users).filter( or_( Users.id < 2, and_(Users.name == 'eric', Users.id > 3), Users.extra != "" )).all() # 7. filter_by session.query(Users).filter_by(name='alex').all() # 8. 通配符 ret = session.query(Users).filter(Users.name.like('e%')).all() #e% 以e開頭的全部,e_ 以e開頭的一個 ret = session.query(Users).filter(~Users.name.like('e%')).all() #~ 指 not in # 9. 切片(限制) result = session.query(Users)[1:2] # 10.排序 ret = session.query(Users).order_by(Users.name.desc()).all() ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() # 11. group by #根據聚合索引進行二次查詢要用having from sqlalchemy.sql import func ret = session.query( Users.depart_id, func.count(Users.id), ).group_by(Users.depart_id).all() for item in ret: print(item) from sqlalchemy.sql import func ret = session.query( Users.depart_id, func.count(Users.id), ).group_by(Users.depart_id).having(func.count(Users.id) >= 2).all() for item in ret: print(item) # 12.union 和 union all """ select id,name from users UNION select id,name from users; """ q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union(q2).all() #union上下拼接去重 q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union_all(q2).all() #union_all 上下拼接不去重 ,join左右拼接