Steps to use ORM to add data in MySQL

【Foreword】

If you want to use ORM to operate data in the database, the premise is that you have created a new ORM model; that is, the model we have built before https://www.jb51.net/article/218036.htm

[ORM operation steps]

• Constructing ORM model objects
• Add to session
• Submit to database
• If an exception occurs, roll back the transaction (optional)

【Constructing ORM model objects】

user_obj = User(
username="use1",
password="123456",
real_name = "User 1",
age=12
)

【Add to session】

# Add an object session.add(user_obj)

# Add multiple objects session.add_all([user1,user2,user3])

[The role of session]

• Establishing a session with the database
• Use session to add, delete, modify and query data in the database
• Use session for transaction control (commit and rollback)
• You need to close it after use session.close()

[Creating a session]

There are two methods, the following code example

# Method 1: Instantiate session
from sqlalchemy.orm import Session

with Session(engine) as session:
    session.add(User())
    session.commit()

# Method 2: Create a factory function from sqlalchemy.orm import sessionmaker

Session = sessionmaker(engine)

with Session.begin() as session:
    session.add(User())

[Submit data to database]

with Session(engine) as session:
    session.add(user_obj)
    session.add_all([user1,user1,user1])
    session.commit()

[Exception occurred, rollback transaction]

with Session(engine) as session:
    session.begin()
    try:
        session.add(user1)
        session.add(user2)
    except:
        session.rollback()
        raise
    else:
        session.commit()

[Other common methods in Session objects]

1. execute(statement, params=None,*args) executes SQL query

2. delete(instance) physically deletes data

3. get(entity,idnet,*args) returns the ORM object that meets the conditions according to the primary key/None

4. query(*entities,**kwargs)

Use ORM query to return Query object

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