Flask中的的SQLAlchemy

很久沒有更新Blog了

今天來聊一聊 Python 的 ORM 框架 SQLAlchemy 有的孩子已經據說過這個框架的大名了,也據說了 SQLAlchemy 沒有 Django 的 Models 好用

我在這裏闢謠一下, Models 牢牢只是配置和使用比較簡單,由於他是Django自帶的ORM框架,也正是由於是Django原生的,因此兼容性遠遠不如SQLAlchemy

真正算得上全面的ORM框架是咱們的SQLAlchemy ORM框架,它能夠在任何使用SQL查詢時使用

固然了,不管是使用什麼ORM框架,都是爲了方便不熟練數據庫的同窗使用的,我的仍是比較推崇原生 SQL 哈

ok，咱們來看一下 SQLAlchemy 如何使用:

1.建立表的一波說不出來但很牛x的操做

#create_table.py 
#經過SQLAlchemy建立數據表
# 1.導入SQLAlchemy，沒安裝的記得安裝一下啊
from sqlalchemy.ext.declarative import declarative_base

# 2.建立ORM模型基類
Base = declarative_base()  # 至關於Django Model

# 3.導入ORM對應數據庫數據類型的字段
from sqlalchemy import Column, Integer, String


# 4.建立ORM對象
class User(Base):
    __tablename__ = "user"
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(32), index=True)


# 5.建立數據庫鏈接
from sqlalchemy import create_engine

#mysql+pymysql用mysql數據庫+pymysql，root用戶，614615數據庫密碼，@127.0.0.1本地地址，3306數據庫端口號，led數據庫名，剩下的是字符編碼，這要是不懂，滾！！！
engine = create_engine("mysql+pymysql://root:614615@127.0.0.1:3306/led?charset=utf8")
# 數據庫鏈接建立完成

# 6.去數據庫中建立與User所對應的數據表
# 去engine數據庫中建立全部繼承Base類的 ORM對象
Base.metadata.create_all(engine)

2.增的操做

#curd_insert.py

# 增
# 1.打開數據庫的連接
from create_table import engine
# 2.建立繪畫
from sqlalchemy.orm import sessionmaker
# 3.建立會話的窗口
Session = sessionmaker(engine)
# 4.打開會話窗口
db_session = Session()
from create_table import User
with open('name.txt','r')as f:
    for i in f.read():
        db_session.add_all([
            User(name=i),
        ])

        db_session.commit()
        db_session.close()
#這裏說一下，add和add_all的區別，就是單挑和多條的差距，固然，add_all也能夠插入單條，只不過消耗的資源多一些，

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3.5改的高級操做

#curd_update_more.py

from sqlalchemy.orm import sessionmaker
from create_table import User,engine
Session = sessionmaker(engine)
db_session = Session()

#直接修改
db_session.query(User).filter(User.id > 10).update({"name":"001"})
db_session.commit()
db_session.close()


#原有值的基礎上添加 -2
db_session.query(User).filter(User.id > 0).update({User.name:User.name + "-2"},synchronize_session=False)
db_session.commit()
db_session.close()

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3.改的操做

#curd_update.py


# 更新

from sqlalchemy.orm import sessionmaker
from create_table import User,engine
Session = sessionmaker(engine)
db_session = Session()

ret = db_session.query(User).filter(User.name == "李志強").update({"name":"好人"})
db_session.commit()#切記！！執行語句
db_session.close()#關閉會話




ret = db_session.query(User).filter(User.id >=60).update({"name":"我是好人"})
db_session.commit()
db_session.close()

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4.查的操做

#curd_select.py

#查

from create_table import engine
from create_table import User
from sqlalchemy.orm import sessionmaker

Session = sessionmaker(engine)
db_session = Session()

# 1.簡單的查詢
res = db_session.query(User).all()
for i in res:
    print(i.name)

res_list = db_session.query(User).first()
print(res_list.id)


# 2.有條件的查詢
ret = db_session.query(User).filter(User.name == "李二短").first()
# 由於這裏查到一個因此不會用索引取值
print(ret.name,ret.id)

ret = db_session.query(User).filter(User.name == "浩").all()
# 這裏查到全部因此會用索引取值第一個
print(ret[0].name,ret[0].id)

ret = db_session.query(User).filter(User.id >= 60).all()
# 這裏說一下，查詢全部的id>=60的，查詢全部進行遍歷取值
for i in ret:
    print(i.name,i.id)


# 查看原生的sql語句辦法
ret = db_session.query(User).filter(User.id >= 60)
print(ret)

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5.刪除的操做

curd_delete.py
# 刪除

from sqlalchemy.orm import sessionmaker
from create_table import engine,User

Session = sessionmaker(engine)
db_session = Session()

ret = db_session.query(User).filter(User.name == "我是好人").delete()
db_session.commit()
db_session.close()
# print(ret)


ret = db_session.query(User).filter(User.id >= 20).delete()
db_session.commit()
db_session.close()
# print(ret)

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二.一對多的表關係操做ForeginKey

1.建立一對多的表關係

#create_table_ForeginKey.py


# 一對多建表操做
from  sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
from sqlalchemy import create_engine
from sqlalchemy import Column,Integer,String,ForeignKey
from sqlalchemy.orm import relationship


class School(Base):
    __tablename__ = 'school'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))


class Student(Base):
    __tablename__ = 'student'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    school_id = Column(Integer,ForeignKey("school.id"))
    stu2sch = relationship("School",backref="stu2sch")

engine = create_engine("mysql+pymysql://root:614615@127.0.0.1:3306/led?charset=utf8")

Base.metadata.create_all(engine)

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2.增長數據

#curd_insert_ForeginKey.py

#添加數據
from sqlalchemy.orm import sessionmaker
from create_table_ForeignKey import Student,School,String,Integer,engine

Session = sessionmaker(engine)
db_session = Session()


# 正向的添加數據 relationship版本
sch_obj = School(name="清華")
sch_obj.stu2sch = [Student(name="李志強"),Student(name="李二短")]
db_session.add(sch_obj)
db_session.commit()
db_session.close()



#反向的添加數據 relationship版本
stu_obj = Student(name="龍龍",stu2sch=School(name="北大"))
db_session.add(stu_obj)
db_session.commit()
db_session.close()

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3.修改操做

curd_update_ForeginKey.py

from sqlalchemy.orm import sessionmaker
from create_table_ForeignKey import School,Student,String,Integer,engine

Session = sessionmaker(engine)
db_session = Session()

sch = db_session.query(School).filter(School.name == "清華").first()
# 查到學校的id，在學生表裏查到學生是龍龍的學生把學校id改爲察到的學校id
db_session.query(Student).filter(Student.name == "龍龍").update({"school_id":sch.id})
db_session.commit()
db_session.close()

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4.查的操做

#curd_select_ForeginKey.py

from sqlalchemy.orm import sessionmaker
from create_table_ForeignKey import School,Student,engine,String,Integer

Session = sessionmaker(engine)
db_session = Session()


#relationship正向查詢版本
stu = db_session.query(Student).all()
for i in stu:
    print(i.name,i.id,i.stu2sch.name)


# relationship反向查詢版本
sch = db_session.query(School).all()
for school in sch:
    for student in school.stu2sch:
        print(school.id,school.name,student.name)

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5.delete

#curd_delete_ForeginKey.py

from sqlalchemy.orm import sessionmaker
from create_table_ForeignKey import Student,School,String,Integer,engine

Session = sessionmaker(engine)
db_session = Session()

sch = db_session.query(School).filter(School.name == '北大').first()
print(sch.id)
db_session.query(Student).filter(Student.school_id == sch.id).delete()
db_session.commit()
db_session.close()

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三。多對多表的操做

未完，待續