Basic use of Sqlalchemy

rely on

pip install sqlalchemy

Basic use

from sqlalchemy.orm import Session, sessionmaker, declarative_base
from sqlalchemy import create_engine, Column, Integer, String

# 1. Create the engine 
engine = create_engine('mysql+pymysql://root:[email protected]/sqlalchemy_test')

# 2. Create a session 
# 2.1  Basic creation method 
# s = Session(bind=engine)

# 2.2  adopt sessionmaker establish , In essence Session, It's just that you can customize the configuration 
# Session = sessionmaker(bind=engine)
# s = Session()

# 2.3  adopt scoped_session establish ,  Pass in a session factory 
Session =scoped_session(sessionmaker(bind=engine))
s = Session()


# 3. establish ORM Mapping base class 
Base = declarative_base()


# 4. Create data table 
class User(Base):
    __tablename__ = 'user_account'
    id = Column(Integer, primary_key=True)
    name = Column(String(25))

    def __repr__(self):
        return f'User(id={
      self.id}, name={
      self.name})'


# 5. Create if it does not exist , If it exists, it doesn't create 
Base.metadata.create_all(engine)

# 6. Instantiate a Use object 
# user = User(name='chatu')

# 7. take User Object added to Session in 
s.add(user)
# 8. Commit to database 
s.commit()
# 9. close session object 
s.close()

More database operations

from add import s, User, engine  #  What is imported here is defined above 
from sqlalchemy import select, table, update, insert, delete, create_engine, column

# result = s.query(User).all()
# print(result)

# s.scalars() Execute statement , And return instance objects 
#  Can pass select This kind of native , Then go ahead and do 
#  It can also be done through session.query To screen 
# s.execute() You can add, delete, modify and query 


# #####  Near native sqlalchemy Inquire about 
print(type(select(User)))
#  lookup 
sel = select(User).where(User.name == 'chatu1')
print(type(select(User).where(User.name == 'chatu1')))
result = s.execute(sel)
print(result, '=============', type(result))
for i in result:
    print(i)

print('---------------------',s.scalars(sel))
for i in s.scalars(sel):
    print(i)

#  to update 
upd = (update(User).
where(User.id == 4).
values(name='chst1122')
)

#  Directly through engine The created connection is executing execute Will be submitted to the database 
# conn = engine.connect()
# conn.execute(upd)

#  adopt session perform execute
a = s.execute(upd)  #  Perform the update 
s.commit()  #  The database will not be updated until it is committed 

#  Insert 
ins = insert(User).values(name='hello world')
s.execute((ins))
s.commit()

#  Delete 
delete_data = delete(User).where(column('id') >= 100)
s.execute(delete_data)
s.commit()


######  Use the session mechanism to query 

#  Inquire about 
filter_query = s.query(User).filter(User.name=='chatu1').all()  #  Return a list , Include all filtered objects 
# filter_query = s.query(User).filter(User.name.in_(['chatu2'])).all() #  Return a list , Include all filtered objects 
print(filter_query)

#  modify 
update_filter = s.query(User).filter(User.name=='chatu1').update({
    'name':'chatu11'})
s.commit()

#  add to 
user = User(name='hello chatu')
s.add(user)
s.commit()

#  Delete 
s.query(User).filter(User.name=='chst1122').delete()
s.commit()

appendix

1. link ：Session、sessionmaker、scoped_session Related information
2. Near native sqlalchemy operation
link - Inquire about ：sqlalchemy- Inquire about
link - to update , Insert , Delete ：sqlalchemy- to update , Insert , Delete
3. Conversation through query The operation of the operation database
The session query Inquire about ：query operation API