SQLAlchemy Tutorial
SQLAlchemy Core
SQLAlchemy ORM
SQLAlchemy Useful Resources
Selected Reading
SQLAlchemy Core
- Using Set Operations
- Using Functions
- Using Conjunctions
- Using Joins
- Multiple Table Deletes
- Parameter-Ordered Updates
- Using Multiple Table Updates
- Using Multiple Tables
- Using DELETE Expression
- Using UPDATE Expression
- Using Aliases
- Using Textual SQL
- Selecting Rows
- Executing Expression
- SQL Expressions
- Creating Table
- Connecting to Database
- Expression Language
SQLAlchemy ORM
- Dialects
- Many to Many Relationships
- Deleting Related Objects
- Eager Loading
- Common Relationship Operators
- Working with Joins
- Working with Related Objects
- Building Relationship
- Textual SQL
- Returning List and Scalars
- Filter Operators
- Applying Filter
- Updating Objects
- Using Query
- Adding Objects
- Creating Session
- Declaring Mapping
SQLAlchemy Useful Resources
Selected Reading
- Who is Who
- Computer Glossary
- HR Interview Questions
- Effective Resume Writing
- Questions and Answers
- UPSC IAS Exams Notes
Creating Session
SQLAlchemy ORM - Creating Session
In order to interact with the database, we need to obtain its handle. A session object is the handle to database. Session class is defined using sessionmaker() – a configurable session factory method which is bound to the engine object created earper.
from sqlalchemy.orm import sessionmaker Session = sessionmaker(bind = engine)
The session object is then set up using its default constructor as follows −
session = Session()
Some of the frequently required methods of session class are psted below −
| Sr.No. | Method & Description |
|---|---|
| 1 | begin() begins a transaction on this session |
| 2 | add() places an object in the session. Its state is persisted in the database on next flush operation |
| 3 | add_all() adds a collection of objects to the session |
| 4 | commit() flushes all items and any transaction in progress |
| 5 | delete() marks a transaction as deleted |
| 6 | execute() executes a SQL expression |
| 7 | expire() marks attributes of an instance as out of date |
| 8 | flush() flushes all object changes to the database |
| 9 | invapdate() closes the session using connection invapdation |
| 10 | rollback() rolls back the current transaction in progress |
| 11 | close() Closes current session by clearing all items and ending any transaction in progress |