Django’s ORM (Object-Relational Mapping) provides a convenient and powerful way to interact with databases. It allows you to query, create, update, and delete records using Python syntax. Here’s an overview of querying the database using Django’s ORM:

1. Retrieving Objects:

• To retrieve objects from the database, you can use the objects attribute of a model class.
• For example, to retrieve all objects of a model, you can use Model.objects.all().
• You can filter the objects based on specific criteria using the filter() method.
• For more complex queries, you can use the Q object and logical operators (| for OR, & for AND).
• Additional methods like exclude(), get(), and first() allow you to retrieve specific objects.

1. Chaining Querysets:

• Querysets can be chained together to narrow down the results further.
• For example, you can apply multiple filters using the filter() method one after the other.
• Chaining allows you to build complex queries step by step.

1. Querying Related Objects:

• Django’s ORM provides a way to query related objects using relationships defined in models.
• You can access related objects through fields like ForeignKey, OneToOneField, or ManyToManyField.
• For example, if you have a related model called RelatedModel with a foreign key to Model, you can query related objects using model_instance.relatedmodel_set.all().

1. Querying with Aggregates:

• Django’s ORM supports aggregations, allowing you to perform calculations on query results.
• Aggregation functions include count(), sum(), avg(), min(), and max().
• You can annotate querysets with aggregated values using the annotate() method.

1. Ordering Querysets:

• You can specify the order in which objects should be retrieved using the order_by() method.
• Use the field names to specify the ordering (prefixed by - for descending order).
• Multiple fields can be specified for complex ordering.

1. Querying with Raw SQL:

• Django’s ORM allows you to execute raw SQL queries when needed.
• Use the raw() method to execute raw SQL queries and retrieve results as model instances.

1. Executing Queries:

• Querysets are lazy, meaning the database query is executed only when the data is accessed.
• Use methods like first(), count(), or iterate over the queryset to trigger the database query.
• To improve performance, you can select specific fields using the values() or values_list() methods.

Django’s ORM provides a powerful and expressive way to query the database without writing raw SQL. It abstracts the underlying database and allows you to work with models and relationships using Python code. For more detailed information and advanced querying options, refer to the Django documentation on querying the database: https://docs.djangoproject.com/en/3.2/topics/db/queries/.