Add README files to all examples and fix minor typo bugs

# Object-Relational Mapping Examples

In this repository are available some easy Object-Relational Mapping (ORM) examples.

For more details, please refer to the _Lecture 6 – Data Model Implementation_ of the _Open Data Management & the Cloud_ course.

# Django Example

Create the anaconda environment for this example

    conda create -n insurance django

To activate this environment, use

    conda activate insurance

Additional packages are needed, not available in Anaconda but installed with the `pip` command

    pip install django-extensions djangorestframework

    pip install django-composite-field django-url-filter

    pip install django-phonenumber-field phonenumbers

    pip install Pillow

To deactivate an active environment, use

    conda deactivate

## Create a Django Project

Run the following commands

    django-admin startproject insurance

    cd insurance

    python manage.py startapp insurancedb

which create a project folder, named insurance, with additional files and then an application, named insurancedb, inside the project.

It automatically creates skeleton files needed by a Django project and application.

Copy the `admin.py` and `models.py` files to the `insurancedb` folder

    cp ../admin.py insurancedb/

    cp ../models.py insurancedb/

and copy the `urls.py` and `views.py` file to the `insurance` folder

    cp ../urls.py insurance/

    cp ../views.py insurance/

Edit the `insurance/setting.py` file adding in the `INSTALLED_APPS` list

two more elements: `django_extensions` and `insurancedb`. Then your

application definition should appear like this

    INSTALLED_APPS = [

        'django.contrib.admin',

        'django.contrib.auth',

        'django.contrib.contenttypes',

        'django.contrib.sessions',

        'django.contrib.messages',

        'django.contrib.staticfiles',

        'django_extensions',

        'insurancedb',

    ]

Finally, generate a migration and migrate

    python manage.py makemigrations

    python manage.py migrate

Insert some data

    python manage.py shell < ../insert.py

Create an admin user

    python manage.py createsuperuser

Run the Django web server

    python manage.py runserver

Access to <http://127.0.0.1:8000>.

# ORM Example - Euclid

# ORM Example - Euclid

    git clone https://www.ict.inaf.it/gitlab/odmc/orm_example.git

Create the anaconda environment for this example

    cd orm_example/euclid_example

Crea l'ambiente di anaconda

    conda create -n euclid_example django

To activate this environment, use

    conda create -n euclid_example

    conda activate euclid_example

    conda activate euclid_example

    pip install django-extensions djangorestframework django-composite-field django-url-filter

python manage.py migrate

Additional packages are needed, not available in Anaconda but installed with the `pip` command

python manage.py shell

    pip install django-extensions djangorestframework

    pip install django-composite-field django-url-filter

python manage.py runserver

To deactivate an active environment, use

    conda deactivate

add admin password

## Run the Django Project

## Start from scratch

Apply migrations

    django-admin startproject euclid_example

    python manage.py migrate

    cd euclid_example

    python manage.py startapp imagedb

Also in settings.py you have to add the name of the app imagedb

Create an admin user

In the imagedb/models.py add the data model classes

    python manage.py createsuperuser

Once we have defined our data model in imagedb/models.py we need Django to create the corresponding DB schema

You can access the database throught the Django shell

    python manage.py shell

or running the Django web server

    python manage.py runserver

python manage.py makemigrations

then access to <http://127.0.0.1:8000/admin>.

# SQLAlchmy Examples

Create the anaconda environment for this set of examples

Create the anaconda environment for this set of examples

    conda create -n orm_sqlalchemy sqlalchemy

    conda create -n orm_sqlalchemy sqlalchemy

## # To activate this environment, use

To activate this environment, use

#

#     $ conda activate orm_sqlalchemy

#

# To deactivate an active environment, use

#

#     $ conda deactivate

    conda activate orm_sqlalchemy

To deactivate an active environment, use

    conda deactivate

## Example 1

In this first example we are going to map a single _Car_ table.

Each _Car_ has an integer _id_ as primary key, a _name_ and a _price_.

Enter the `example_1` directory

    cd example_1

All the SQLAlchmy components

(engine, declarative base class, mapping and session class)

are configured in the `mapping.py` file.

Create the database

    python create.py

the SQLite file `example_1.db` has been created.

Now insert some data

    python insert.py

Select all data in the database

    python read.py

and perform some queries filtered by car name, by id or by car price

    python filter.py

Exit from the example_1 directory

    cd ..

## Example 2

In this second example we are going to map two tables, _Author_ and _Book_,

connected with a one-to-many relation.

Each _Author_ has an integer _id_ as primary key and a _name_.

Eack _Book_ has an integer _id_ as primary key, a _title_ and an *author_id* as foreign key.

Enter the `example_2` directory

    cd example_2

All the SQLAlchmy components

(engine, declarative base class, mapping, relationship and session class)

are configured in the `mapping.py` file.

Create the database

    python create.py

the SQLite file `example_2.db` has been created.

Now insert some data

    python insert.py

Perform some queries selecting all books by an author or a book to get its author

    python filter.py

Exit from the example_2 directory

    cd ..

**WARNING**

In SQLite you have to enable foreign key constraint executing

    PRAGMA foreign_keys=ON;

## Example 3

In this third example we are going to map inheritance with three tables, _Client_, _Person_ and _Company_, where a _Client_ can be a _Person_ or a _Company_.

Each _Client_ has an integer _id_ as primary key, an _address_ and a _type_.

Each _Person_ has an integer _id_ as primary foreign key, a _name_ and a _surname_.

Each _Company_ has an integer _id_ as primary foreign key, a _company_name_ and a _industry_.

The _type_ discriminates if the _Client_ is also a _Person_ or a _Company_. The _id_ is unique among _Client_, _Person_ and _Company_.

Enter the `example_3` directory

    cd example_3

All the SQLAlchmy components

(engine, declarative base class, mapping, relationship and session class)

are configured in the `mapping.py` file.

Create the database

    python create.py

the SQLite file `example_3.db` has been created.

Now insert some data

    python insert.py

Perform some queries selecting all clients by address or only clients which are persons by address

    python filter.py

Exit from the example_3 directory

    cd ..

    id = Column(Integer, primary_key=True)

    id = Column(Integer, primary_key=True)

    title = Column(String)      

    title = Column(String)      

    author_id = Column(Integer, ForeignKey("Author.id"))

    author_id = Column(Integer, ForeignKey("author.id"))

    author = relationship("Author")

    author = relationship("Author")