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https://github.com/fredrikaverpil/sqlalchemy-orm


https://github.com/fredrikaverpil/sqlalchemy-orm

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README 

        
# sqlalchemy-orm



Working examples from https://auth0.com/blog/sqlalchemy-orm-tutorial-for-python-developers/



## Quickstart



* Run `docker-compose up`

* Configure db through pgadmin (described under "Postgresql & PgAdmin powered by compose" further down below)

* Run:



```bash

python -m venv .venv

source .venv/bin/activate

pip install -r requirements.txt -r requirements-dev.txt



python src/inserts.py  # populate the database

python src/queries.py  # perform queries

```



Output from `queries.py`:



```

### All movies:

The Bourne Identity was released on 2002-10-11

Furious 7 was released on 2015-04-02

Pain & Gain was released on 2013-08-23



### Recent movies:

Furious 7 was released after 2015



### Dwayne Johnson movies:

The Rock starred in Pain & Gain

The Rock starred in Furious 7



### Actors that live in Glendale:

Dwayne Johnson has a house in Glendale

Mark Wahlberg has a house in Glendale

```



## Notes on SQLAlchemy ORM



* SQLAlchemy expose interfaces in accordance with the Python DBAPI, specified in [PEP-249](https://www.python.org/dev/peps/pep-0249/)

* PostgreSQL, MySQL, Oracle, Microsoft SQL Server, and SQLite can be used with SQLAlchemy

* Psycopg fully implements the Pyhton DBAPI implementation for PostgreSQL

* SQLAlchemy supports various [SQL dialects](http://docs.sqlalchemy.org/en/latest/dialects/)

* SQLAlchemy supports [generic types](https://docs.sqlalchemy.org/en/14/core/type_basics.html#generic-types), [vendor types](https://docs.sqlalchemy.org/en/14/core/type_basics.html#sql-standard-and-multiple-vendor-types) and [custom types](https://docs.sqlalchemy.org/en/14/core/custom_types.html)

* SQLAlchemy supports four types of relationships:

  * [One to many](http://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#one-to-many)

  * [Many to one](http://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#many-to-one)

  * [One to one](http://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#one-to-one)

  * [Many to many](http://docs.sqlalchemy.org/en/latest/orm/basic_relationships.html#many-to-many)

* SQLAlchemy ORM [cascading](http://docs.sqlalchemy.org/en/latest/orm/cascades.html) are handled through the `relationship()` construct. The most common cascade strategies:

  * `save-update`: Indicates that when a parent object is saved/updated, child objects are saved/updated as well.

  * `delete`: Indicates that when a parent object is deleted, children of this object will be deleted as well.

  * `delete-orphan`: Indicates that when a child object loses reference to a parent, it will get deleted.

  * `merge`: Indicates that merge() operations propagate from parent to children.

* SQLAlchemy ORM [sessions](http://docs.sqlalchemy.org/en/rel_1_1/orm/session_basics.html) is used to maintain a list of objects affected by a business transaction and to coordinate the writing out of these changes

* The Query API provides dozens of useful functions like `all()`. In the following list, we can see a brief explanation about the most important ones:

  * `count()`: Returns the total number of rows of a query.

  * `filter()`: Filters the query by applying a criteria.

  * `delete()`: Removes from the database the rows matched by a query.

  * `distinct()`: Applies a distinct statement to a query.

  * `exists()`: Adds an exists operator to a subquery.

  * `first()`: Returns the first row in a query.

  * `get()`: Returns the row referenced by the primary key parameter passed as argument.

  * `join()`: Creates a SQL join in a query.

  * `limit()`: Limits the number of rows returned by a query.

  * `order_by()`: Sets an order in the rows returned by a query.



# Postgresql & PgAdmin powered by compose



This part of the project was forked from: https://github.com/khezen/compose-postgres



## Requirements:

* docker >= 17.12.0+

* docker-compose



## Quick Start

* Clone or download this repository

* Go inside of directory,  `cd compose-postgres`

* Run this command `docker-compose up -d`



## Environments

This Compose file contains the following environment variables:



* `POSTGRES_USER` the default value is **postgres**

* `POSTGRES_PASSWORD` the default value is **changeme**

* `PGADMIN_PORT` the default value is **5050**

* `PGADMIN_DEFAULT_EMAIL` the default value is **[email protected]**

* `PGADMIN_DEFAULT_PASSWORD` the default value is **admin**



## Access to postgres: 

* `localhost:5432`

* **Username:** postgres (as a default)

* **Password:** changeme (as a default)



## Access to PgAdmin: 

* **URL:** `http://localhost:5050`

* **Username:** [email protected] (as a default)

* **Password:** admin (as a default)



## Add a new server in PgAdmin:

* **Host name/address** `postgres`

* **Port** `5432`

* **Username** as `POSTGRES_USER`, by default: `postgres`

* **Password** as `POSTGRES_PASSWORD`, by default `changeme`