python/flask/數據庫/sqlalchemy

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

安裝

pip3 install sqlalchemy

• 使用 - - 單表操作

• 執行原生SQL語句

創建表

win使用navicat 或者使用sql語句進行創建

• 單表 原生sql 創建連接及查詢

import threading
import sqlalchemy
from sqlalchemy import create_engine
 
engine = create_engine(
    "mysql+pymysql://root:[email protected]:3306/db1?charset=utf8",
    max_overflow=0,  # 超過連接池大小外最多創建的連接
    pool_size=5,  # 連接池大小
    pool_timeout=30,  # 池中沒有線程最多等待的時間，否則報錯
    pool_recycle=-1  # 多久之後對線程池中的線程進行一次連接的回收（重置）
)
 
conn = engine.raw_connection()
cursor = conn.cursor()
cursor.execute(
    "select * from t1"
)
result = cursor.fetchall()
cursor.close()
conn.close()

• ORM 單表 操作 – 連接方式(2種)

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Student
from threading import Thread

engine = create_engine(
    "mysql+pymysql://root:[email protected]:3306/day120?charset=utf8",
    max_overflow=0,   # 超過連接池大小外最多創建的連接
    pool_size=5,      # 連接池大小
    pool_timeout=30,  # 池中沒有線程最多等待的時間，否則報錯
    pool_recycle=-1   # 多久之後對線程池中的線程進行一次連接的回收（重置）
)
# ############### 方式 1 ##################
SessionFactory = sessionmaker(bind=engine)

def task():
	session = SessionFactory()
	ret = session.query(Student).all()
	return ret
	session.close()  # 把連接還到連接池
	
# ############### 方式 2 ################## 
# 實現原理就是內部 實現 theding_local(0
SessionFactory = sessionmaker(bind=engine)
session = scoped_session(SessionFactory)
def task():
	ret = session.query(Student).all()
	return ret
	session.remove()  # 把連接還到連接池
	
for i in range(10):
	t = Thread(target=task)
	t.start()

• ORM 單表 操作

創建表 models

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column
from sqlalchemy import Integer, String, Text, Date, DateTime
from sqlalchemy import create_engine

Base = declarative_base()


class Users(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=False)


def create_all():
    engine = create_engine(
        "mysql+pymysql://root:[email protected]:3306/s9day120?charset=utf8",
        max_overflow=0,  # 超過連接池大小外最多創建的連接
        pool_size=5,  # 連接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，否則報錯
        pool_recycle=-1  # 多久之後對線程池中的線程進行一次連接的回收（重置）
    )

    Base.metadata.create_all(engine)


def drop_all():
    engine = create_engine(
        "mysql+pymysql://root:[email protected]:3306/s9day120?charset=utf8",
        max_overflow=0,  # 超過連接池大小外最多創建的連接
        pool_size=5,  # 連接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，否則報錯
        pool_recycle=-1  # 多久之後對線程池中的線程進行一次連接的回收（重置）
    )
    Base.metadata.drop_all(engine)


if __name__ == '__main__':
    create_all()

• 表單 增/刪/改/查

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="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)  #字符串的拼接
session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") #數字的相加
session.commit()
"""
# ################ 查詢 ################
"""
r1 = session.query(Users).all()
r2 = session.query(Users.name.label('別名'), Users.age).all()	  # 別名 == as
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()

• 單表 查詢條件 詳解

#　################ 條件 filter 和 ftilter_by ################
'''
ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()  # 表達式
ret = session.query(Users).filter_by(name='alex').all()  # 參數 ,filter_by其實內部也會轉成
'''

# filter(括號)表示 and
ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()

# ################ between ################
ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()

# ################ in ################
ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()

# ################ not in == ~ ################
ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()

# ################ 子查詢 ################
ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter(name='eric'))).all()

# ################ and 和 or 聯合使用 ################
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 ################
#	 %代表多個字符    _(下劃線)代表1個字符
ret = session.query(Users).filter(Users.name.like('e%')).all()
ret = session.query(Users).filter(~Users.name.like('e%')).all()

# ################ 限制 切片  分頁 ################
ret = session.query(Users)[1:2]

# ################ 排序 order_by ################
ret = session.query(Users).order_by(Users.name.desc()).all()  # desc 從大到小
ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()  # name從大到小, id 從小到大

# ################ 分組  ################
from sqlalchemy.sql import func

ret = session.query(Users).group_by(Users.id).all()
ret = session.query(
    func.max(Users.id),		 #分組後對id取大還是取小
    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()   # 根據聚合函數進行二次篩選只能用having

# ################ 連表 (默認爲內連接)################

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() # isout=True 左連接

# ################ 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()  		 # 兩個表上下拼接  union 去重   (類似於join左右拼接)

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() 是不去重

組合對應sql
select id,name from t1 
union
select id,name from t1;

• m2m 聯表操作 - 創建表 - - 用戶表及部門表 (記錄先用Navicat添加)
• 基於 ForeignKey 操作 relationship

# models

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column
from sqlalchemy import Integer, String, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine

Base = declarative_base()


# 創建部門表
class Depart(Base):
    __tablename__ = 'depart'

    id = Column(Integer, primary_key=True)
    title = Column(String(32), index=True, nullable=False)


# 用戶表
class Users(Base):
    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=False)
    depart_id = Column(Integer, ForeignKey('depart.id')) 	# ForeignKey

    dp = relationship('Depart', backref='pers') 	# ralationship 用於反向查找


def create_all():
    engine = create_engine(
        "mysql+pymysql://root:[email protected]:3306/day120?charset=utf8",
        max_overflow=0,
        pool_size=5,
        pool_timeout=10,
    )

    Base.metadata.create_all(engine)


if __name__ == '__main__':
    create_all()

使用 - - 多表操作 - - 增/刪/改/查

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Users, Depart

engine = create_engine(
    "mysql+pymysql://root:[email protected]:3306/day120?charset=utf8",
    max_overflow=0,  # 超過連接池大小外最多創建的連接
    pool_size=5,  # 連接池大小
    pool_timeout=30,  # 池中沒有線程最多等待的時間，否則報錯
    pool_recycle=-1  # 多久之後對線程池中的線程進行一次連接的回收（重置）
)
SessionFactory = sessionmaker(bind=engine)
session = SessionFactory()


'''
# *************** 增 ***************
d1 = Depart(title='運維部')
d1.pers = [Users(name='D1'), Users(name='D1'), Users(name='D1')]  # 增加多個用戶,在同一個部門
session.add(d1)
session.commit()



 *************** 查  ***************
# ralationship 正向查找
# ret = session.query(Users).all()
# for row in ret:
#     print(row.id, row.name, row.dp.title)

# ralationship 反向查找
ret = session.query(Depart).filter(Depart.title == '銷售').first()

for row in ret.pers:
    print(row.id, row.name, row.dp.title)
'''

• m2m - - 多表操作 - 聯合唯一

# 創建表 models

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column
from sqlalchemy import Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine

Base = declarative_base()

class Student(Base):
    __tablename__ = 'student'

    id = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=False)

	course_list = relationship('Course',secondary='Student2Course', backref='student_list)  # 基於 Student2Course 關聯 Course表


class Course(Base):
    __tablename__ = 'course'

    id = Column(Integer, primary_key=True)
    title = Column(String(32), index=True, nullable=False)


class Student2Course(Base):
    __tablename__ = 'student2course'

    id = Column(Integer, primary_key=True, autoincrement=True)
    student_id = Column(Integer, ForeignKey('student.id'))
    course_id = Column(Integer, ForeignKey('course.id'))

    __table_args__ = (
        UniqueConstraint('student_id', 'course_id', name='uni_stu_cou'),  # 聯合唯一索引
        # Index('student_id', 'course_id')  # 聯合索引
    )

def create_all():
    engine = create_engine(
        "mysql+pymysql://root:[email protected]:3306/day120?charset=utf8",
        max_overflow=0,
        pool_size=5,
        pool_timeout=10,
    )
    Base.metadata.create_all(engine)

if __name__ == '__main__':
    create_all()

• m2m 基於 relationship 添加表數據 及 創建表關係

# 基於 relationship 創建表關係

obj = Course(title = '英語')
obj.student_list[Student(name='學生三'),Student(name='學生四')]
session.add(obj)
session.commit()
session.close()