python + SQLAlchemy: deleting with the Session object

PythonSqlalchemy

Python Problem Overview


I can't quite figure this out: I'd like to delete all the records from a table on a matching query. Kind of like this.

engine = sqlalchemy.create_engine(string)
meta = MetaData(bind=engine)
meta.reflect(bind=engine, schema='myschema')

Base = automap_base(metadata=meta)
Base.prepare(engine, reflect=True)
Classes = Base.classes

Session = sessionmaker(bind=engine)
session = Session()

session.delete(plays.record_id == '123')

But that isn't working. What's the idea here? Error I get is:

error in parsing record ID 020087: Class 'sqlalchemy.sql.elements.BinaryExpression' is not mapped

Python Solutions


Solution 1 - Python

In SQL Alchemy you are deleting Objects that you get with a query from the database. This you can do in 2 Ways:

Deleting with query (will issue just one DELETE statement):

session.query(User).filter(User.id==7).delete()
session.commit()

Deleting object instance returned by a query (will issue 2 statements: first SELECT, then DELETE):

obj=session.query(User).filter(User.id==7).first()
session.delete(obj)
session.commit()

Solution 2 - Python


Delete All Records

#for all records
session.query(Model).delete()
session.commit()

Deleted Single Row

If you want to delete specific records then try filter clause in the query. ex.

#for specific value
session.query(Model).filter(Model.id==123).delete()
session.commit()

Delete Single Record by Object

record_obj = session.query(Model).filter(Model.id==123).first()
session.delete(record_obj)
session.commit()

https://flask-sqlalchemy.palletsprojects.com/en/2.x/queries/#deleting-records

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Solution 1 - PythonmuthanView Answer on Stackoverflow
Solution 2 - PythonAnand TripathiView Answer on Stackoverflow