SQLAlchemy(3)

一. SQLAlchemy

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。

pip3 install sqlalchemy

流程圖

組成部分

• 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-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

使用

1. 執行原生SQL語句

舉例1

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 t1"
 )
 result = cursor.fetchall()
 cursor.close()
 conn.close()
for i in range(20):
 t = threading.Thread(target=task, args=(i,))
 t.start()

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舉例2

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()

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舉例3

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()

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注意: 查看鏈接 show status like 'Threads%';

2. ORM

a. 建立數據庫表

建立單表

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'

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",
 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 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）
 )

if name == 'main':
 drop_db()
 init_db()
建立單表id </span>= Column(Integer, primary_key=<span style="color: #000000;">True)
name </span>= Column(String(<span style="color: #800080;">32</span>), index=True, nullable=<span style="color: #000000;">False)
# email </span>= Column(String(<span style="color: #800080;">32</span>), unique=<span style="color: #000000;">True)
# ctime </span>= Column(DateTime, <span style="color: #0000ff;">default</span>=<span style="color: #000000;">datetime.datetime.now)
# extra </span>= Column(Text, nullable=<span style="color: #000000;">True)

__table_args__ </span>=<span style="color: #000000;"> (
    # UniqueConstraint(</span><span style="color: #800000;">'</span><span style="color: #800000;">id</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, name=<span style="color: #800000;">'</span><span style="color: #800000;">uix_id_name</span><span style="color: #800000;">'</span><span style="color: #000000;">),
    # Index(</span><span style="color: #800000;">'</span><span style="color: #800000;">ix_id_name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">email</span><span style="color: #800000;">'</span><span style="color: #000000;">),
)Base.metadata.create_all(engine)Base.metadata.drop_all(engine)

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建立多個表幷包含Fk、M2M關係

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
from sqlalchemy.orm import relationship
Base = declarative_base()
##################### 單表示例
class Users(Base):
 tablename = 'users'

class Hosts(Base):
 tablename = 'hosts'

##################### 一對多示例
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_id = Column(Integer, ForeignKey("hobby.id"))

##################### 多對多示例
class Server2Group(Base):
 tablename = 'server2group'
 id = Column(Integer, primary_key=True, autoincrement=True)
 server_id = Column(Integer, ForeignKey('server.id'))
 group_id = Column(Integer, ForeignKey('group.id'))
class Group(Base):
 tablename = 'group'
 id = Column(Integer, primary_key=True)
 name = Column(String(64), unique=True, nullable=False)

class Server(Base):
 tablename = 'server'

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",
 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 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）
 )

if name == 'main':
 drop_db()
 init_db()
建立多個表幷包含Fk、M2M關係id </span>= Column(Integer, primary_key=<span style="color: #000000;">True)
name </span>= Column(String(<span style="color: #800080;">32</span>), index=<span style="color: #000000;">True)
age </span>= Column(Integer, <span style="color: #0000ff;">default</span>=<span style="color: #800080;">18</span><span style="color: #000000;">)
email </span>= Column(String(<span style="color: #800080;">32</span>), unique=<span style="color: #000000;">True)
ctime </span>= Column(DateTime, <span style="color: #0000ff;">default</span>=<span style="color: #000000;">datetime.datetime.now)
extra </span>= Column(Text, nullable=<span style="color: #000000;">True)

__table_args__ </span>=<span style="color: #000000;"> (
    # UniqueConstraint(</span><span style="color: #800000;">'</span><span style="color: #800000;">id</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, name=<span style="color: #800000;">'</span><span style="color: #800000;">uix_id_name</span><span style="color: #800000;">'</span><span style="color: #000000;">),
    # Index(</span><span style="color: #800000;">'</span><span style="color: #800000;">ix_id_name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">extra</span><span style="color: #800000;">'</span><span style="color: #000000;">),
)id </span>= Column(Integer, primary_key=<span style="color: #000000;">True)
name </span>= Column(String(<span style="color: #800080;">32</span>), index=<span style="color: #000000;">True)
ctime </span>= Column(DateTime, <span style="color: #0000ff;">default</span>=<span style="color: #000000;">datetime.datetime.now)# 與生成表結構無關，僅用於查詢方便
hobby </span>= relationship(<span style="color: #800000;">"</span><span style="color: #800000;">Hobby</span><span style="color: #800000;">"</span>, backref=<span style="color: #800000;">'</span><span style="color: #800000;">pers</span><span style="color: #800000;">'</span><span style="color: #000000;">)# 與生成表結構無關，僅用於查詢方便
servers </span>= relationship(<span style="color: #800000;">'</span><span style="color: #800000;">Server</span><span style="color: #800000;">'</span>, secondary=<span style="color: #800000;">'</span><span style="color: #800000;">server2group</span><span style="color: #800000;">'</span>, backref=<span style="color: #800000;">'</span><span style="color: #800000;">groups</span><span style="color: #800000;">'</span><span style="color: #000000;">)id </span>= Column(Integer, primary_key=True, autoincrement=<span style="color: #000000;">True)
hostname </span>= Column(String(<span style="color: #800080;">64</span>), unique=True, nullable=<span style="color: #000000;">False)Base.metadata.create_all(engine)Base.metadata.drop_all(engine)

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指定關聯列：hobby = relationship("Hobby", backref='pers',foreign_keys="Person.hobby_id")

b. 操做數據庫表

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
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)
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()

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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'
 )
 """
 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()
基於scoped_session實現線程安全

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多線程執行示例

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()

for i in range(10):
 t = threading.Thread(target=task, args=(i,))
 t.start()obj1 </span>= Users(name=<span style="color: #800000;">"</span><span style="color: #800000;">alex1</span><span style="color: #800000;">"</span><span style="color: #000000;">)
session.add(obj1)

session.commit()

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基本增刪改查示例

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="wupeiqi"),
 Users(name="alex"),
 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 == "alex").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()
基本增刪改查示例

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經常使用操做

#　條件
ret = session.query(Users).filter_by(name='alex').all()
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()
ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()
from sqlalchemy import and_, or_
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
ret = session.query(Users).filter(Users.name.like('e%')).all()
 ret = session.query(Users).filter(~Users.name.like('e%')).all()
限制
ret = session.query(Users)[1:2]
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()
分組
from sqlalchemy.sql import func
ret = session.query(Users).group_by(Users.extra).all()
 ret = session.query(
 func.max(Users.id),
 func.sum(Users.id),
 func.min(Users.id)).group_by(Users.name).all()
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
ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()
ret = session.query(Person).join(Favor).all()
ret = session.query(Person).join(Favor, isouter=True).all()
組合
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()

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原生SQL語句

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":'wupeiqi'})
 session.commit()
 print(cursor.lastrowid)
session.close()
原生SQL語句

View Code

基於relationship操做ForeignKey

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)
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)
 """
 
 session.close()
基於relationship操做ForeignKey

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基於relationship操做m2m

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組'),
 Group(name='B組'),
 ])
 session.commit()
s2g = Server2Group(server_id=1, group_id=1)
 session.add(s2g)
 session.commit()
gp = Group(name='C組')
 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組'),Group(name='G組')]
 session.add(ser)
 session.commit()
 """
 
使用relationship正向查詢
"""
 v = session.query(Group).first()
 print(v.name)
 print(v.servers)
 """
 
使用relationship反向查詢
"""
 v = session.query(Server).first()
 print(v.hostname)
 print(v.groups)
 """
 
session.close()
基於relationship操做m2m

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其餘

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
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 .name AS group_name, (SELECT count(server.id) AS sid
 FROM server
 WHERE server.id = .id) AS anon_1
 FROM 
 """
 
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()groupgroupgroup

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本文參考連接：

https://www.cnblogs.com/wupeiqi/articles/8259356.html