1.介紹
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。html
pip3 install sqlalchemy
組成部分:python
Engine,框架的引擎 Connection Pooling ,數據庫鏈接池 Dialect,選擇鏈接數據庫的DB API種類 Schema/Types,架構和類型 SQL Exprression Language,SQL表達式語言
SQLAlchemy自己沒法操做數據庫,其必須以來pymsql等第三方插件,Dialect用於和數據API進行交流,根據配置文件的不一樣調用不一樣的數據庫API,從而實現對數據庫的操做,如:mysql
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
django中如何反向生成modelssql
python manage.py inspectdb > app/models.py
2.簡單使用(能建立表,刪除表,不能修改表)
修改表:在數據庫添加字段,類對應上數據庫
1執行原生sql(不經常使用)django
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) ) 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flask
models.py安全
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' # 數據庫表名稱 id = Column(Integer, primary_key=True) # id 主鍵 name = Column(String(32), index=True, nullable=False) # name列,索引,不可爲空 # email = Column(String(32), unique=True) #datetime.datetime.now不能加括號,加了括號,之後永遠是當前時間 # ctime = Column(DateTime, default=datetime.datetime.now) # extra = Column(Text, nullable=True) __table_args__ = ( # UniqueConstraint('id', 'name', name='uix_id_name'), #聯合惟一 # Index('ix_id_name', 'name', 'email'), #索引 ) def init_db(): """ 根據類建立數據庫表 :return: """ engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/aaa?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.create_all(engine) def drop_db(): """ 根據類刪除數據庫表 :return: """ engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/aaa?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()
app.pysession
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) # 每次執行數據庫操做時,都須要建立一個Connection con = Connection() # ############# 執行ORM操做 ############# obj1 = Users(name="lqz") con.add(obj1) # 提交事務 con.commit() # 關閉session,實際上是將鏈接放回鏈接池 con.close()
3.一對多關係
class Hobby(Base): __tablename__ = 'hobby' id = Column(Integer, primary_key=True) caption = Column(String(50), default='籃球') class Person(Base): __tablename__ = 'person' nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) # hobby指的是tablename而不是類名,uselist=False hobby_id = Column(Integer, ForeignKey("hobby.id")) # 跟數據庫無關,不會新增字段,只用於快速鏈表操做 # 類名,backref用於反向查詢 hobby=relationship('Hobby',backref='pers')
4.多對多關係
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) name = Column(String(64), unique=True, nullable=False) # 與生成表結構無關,僅用於查詢方便,放在哪一個單表中均可以 girl = relationship('Girl', secondary='boy2girl', backref='boys')
5.操做數據表
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="lqz") session.add(obj1) # 提交事務 session.commit() # 關閉session session.close()
6.基於scoped_session實現線程安全
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) """ # 線程安全,基於本地線程實現每一個線程用同一個session # 特殊的:scoped_session中有原來方法的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類並無繼承Session,可是卻又它的全部方法 session = scoped_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()
7.基本增刪查改
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: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() """ # ################ 刪除 ################ """ session.query(Users).filter(Users.id > 2).delete() session.commit() """ # ################ 修改 ################ """ #傳字典 session.query(Users).filter(Users.id > 0).update({"name" : "lqz"}) #相似於django的F查詢,這個後面必須配合synchronize_session, #若是是字符串就用False,若是是數字就用#evaluata 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() #只取age列,把name重命名爲xx r2 = session.query(Users.name.label('xx'), Users.age).all() #filter傳的是表達式,filter_by傳的是參數 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 至關於佔位符,用params傳參數 r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all() #自定義查詢sql r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all() """ #增,刪,改都要commit() session.close()
8.經常使用操做
# 條件 ret = session.query(Users).filter_by(name='lqz').all() #表達式,and條件鏈接 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() #注意下劃線 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() #二次篩選 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條件,and_包裹的都是and條件 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開頭,不以e開頭 ret = session.query(Users).filter(Users.name.like('e%')).all() ret = session.query(Users).filter(~Users.name.like('e%')).all() # 限制,用於分頁,區間 ret = session.query(Users)[1:2] # 排序,根據name降序排列(從大到小) ret = session.query(Users).order_by(Users.name.desc()).all() #第一個條件重複後,再按第二個條件升序排 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() # 分組 from sqlalchemy.sql import func ret = session.query(Users).group_by(Users.extra).all() #分組以後取最大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篩選 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() # 連表(默認用forinkey關聯) ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all() #join表,默認是inner join ret = session.query(Person).join(Favor).all() #isouter=True 外連,表示Person left join Favor,沒有右鏈接,反過來便可 ret = session.query(Person).join(Favor, isouter=True).all() #打印原生sql aa=session.query(Person).join(Favor, isouter=True) print(aa) # 本身指定on條件(連表條件),第二個參數,支持on多個條件,用and_,同上 ret = session.query(Person).join(Favor,Person.id==Favor.id, isouter=True).all() # 組合(瞭解)UNION 操做符用於合併兩個或多個 SELECT 語句的結果集 #union和union all的區別? 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()
9.執行原生sql
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() # 查詢 # 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()
10.一對多
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='張三', hobby_id=3), Person(name='李四', hobby_id=4), ]) person = Person(name='張九', hobby=Hobby(caption='姑娘')) session.add(person) #添加二 hb = Hobby(caption='人妖') hb.pers = [Person(name='文飛'), Person(name='博雅')] session.add(hb) session.commit() """ # 使用relationship正向查詢 """ v = session.query(Person).first() print(v.name) print(v.hobby.caption) """ # 使用relationship反向查詢 """ v = session.query(Hobby).first() print(v.caption) print(v.pers) """ #方式一,本身鏈表 # 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:經過relationship person_list=session.query(models.Person).all() for row in person_list: print(row.name,row.hobby.caption) #查詢喜歡姑娘的全部人 obj=session.query(models.Hobby).filter(models.Hobby.id==1).first() persons=obj.pers print(persons) session.close()
11.多對多
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from sql.models import Girl,Boy,Boy2Girl engine = create_engine("mysql+pymysql://root:@127.0.0.1:3307/flask-test?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 添加 ''' session.add_all([ Girl(name='g_com1'), Girl(name='g2.com1'), Boy(name='A組1'), Boy(name='B組2'), ]) session.commit() s2g = Boy2Girl(girl_id=2, boy_id =2) session.add(s2g) session.commit() gp = Boy(name='C組') gp.girl = [Girl(name='c3.com'),Girl(name='c4.com')] session.add(gp) session.commit() ser = Girl(name='c6.com') ser.boys = [Boy(name='F組pp'),Boy(name='G組ll')] session.add(ser) session.commit() ''' """ # 使用relationship正向查詢 """ ''' v = session.query(Boy).first() print(v.name) print(v.girl) ''' # 使用relationship反向查詢 ''' v = session.query(Girl).first() print(v.name) print(v.boys) ''' session.close()
12.其它
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:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 關聯子查詢:correlate(Group)表示跟Group表作關聯,as_scalar至關於對該sql加括號,用於放在後面當子查詢 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, #必須保證這次查詢只有一個值 (select max(id) from xxx) as mid from tb 例如,第三個字段只能有一個值 id name mid 1 lqz 1,2 不合理 2 egon 2 ''' ''' 成績表: id sid cid score 1 1 物理 99 2 1 化學 88 3 2 物理 95 學生表: id name 每一個學生總分數 1 xx 88 2 yy 77 select id,name, (select avr(score) from 成績表 where 成績表.sid=學生表.id) as x from 學生表 subqry = session.query(func.count(成績表.scort).label("sc")).filter(學生表.id == 成績表.sid).correlate(學生表).as_scalar() result = session.query(學生表.name, subqry) ''' # 原生SQL """ # 查詢 cursor = session.execute('select * from users') result = cursor.fetchall() # 添加 cursor = session.execute('insert into users(name) values(:value)',params={"value":'wupeiqi'}) session.commit() print(cursor.lastrowid) """ session.close()
13.Flask-SQLAlchemy
flask和SQLAchemy的管理者,經過他把他們作鏈接架構
db = SQLAlchemy() - 包含配置 - 包含ORM基類 - 包含create_all - engine - 建立鏈接
離線腳本,建立表
詳見代碼
flask-migrate
python3 manage.py db init 初始化:只執行一次
python3 manage.py db migrate 等同於 makemigartions
python3 manage.py db upgrade 等同於migrate
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