Preface : SqlAlchemy is different from flask-SqlAlchemy . flask-SqlAlchemy is the result of flask encapsulating SqlAlchemy. Relatively speaking, flask-SqlAlchemy is more useful, but this article will introduce the use of SqlAlchemy in detail .

Businesses involved in SqlAlchemy:

1: Create a model object, and SqlAlchemy connects to the database

# 创建model对象
class Power(Base):
    __tablename__ = 'power_info'
    id = Column(Integer, primary_key=True, nullable=False)
    uid = Column(String(255), nullable=False)
    power_name = Column(String(255))
    create_time = Column(String(255), nullable=False)
    update_time = Column(String(255))

# SqlAlchemy连接数据库
url = f'mysql+mysqlconnector://{
      
      user}:{
      
      password}@{
      
      host}:{
      
      port}/{
      
      database}'
engine = create_engine(url, echo=True，encoding='utf-8', pool_timeout=30)
#  echo=True 将原生sql语句打印至控制台
# pool_timeout：设置超时时间
# 创建DBSession类型:
DBSession = sessionmaker(bind=engine)
# 创建session对象:
session = DBSession()

2: Find data

Basic syntax:

Find all data:
data = session.query(Field to be searched/can be the entire model object).filter(condition).all()
Find a single piece of data data:
data = session.query(field to be searched/can be the entire model object).filter(condition).one()/first()
More other methods such as: .all() .first() .scalar() .one() .one_or_none() .get() etc. For the difference,
see 【The blogger introduces the differences between these methods in detail】
Conditional query:
conditional query has filter_by and filter methods . For the difference between the two, see 【filter_by / filter difference】. After actual use, I personally feel that filter is more useful

# eg:
data = session.query(Power.id).filter(Power.uid == uid).all()

3: Data sorting

Basic syntax: .order_by(sorting condition.desc()) [desc() descending order, asc() ascending order]

# eg:
# .order_by(Power.create_time.desc())
data = session.query(Power.id).filter(Power.uid == uid).order_by(Power.create_time.desc()).all()

4: Data pagination

Basic syntax: .limit(number of items per page).offset((page number - 1) * number of items per page)
#: Be sure to pay attention here: if the statement also contains sorting statements, be sure to put the paging statement in the sorting after the statement

# eg:
# .limit(page_size).offset((page_index - 1) * page_size)
data = session.query(Power.id).filter(Power.uid == uid).order_by(Power.create_time.desc()).limit(page_size).offset((page_index - 1) * page_size).all()

5: Data update

Basic syntax: session.query(model object).filter(modification condition).update({'database update field name': update value})

# eg:
session.query(Power).filter(Power.uid==uid).update(
        {
    
    'power_name': power_name, 'update_time': update_time})
session.commit()
session.close()

6: Add data:

Basic syntax: variable = model object (the corresponding value of the field in the table to be added)

# eg:
role = Role(uid=uid, role_name=role_name,create_time=create_time, status=Utils.STATUS)
session.add(role)
session.commit()

7: Delete data:

Basic syntax: session.query(model object).filter(delete condition).delete()

# eg:
session.query(RolePower).filter(RolePower.power_uid == uid).delete()
session.commit()

[It is not easy to write an article, please contact the author if you need to forward it! 】

Detailed summary of SqlAlchemy usage