If you have worked with Django, you probably know how user-friendly QuerySets and their filter options can be. QuerySet Filter allows you to retrieve your desired data from the database based on specific criteria you want to extract. Using this capability can significantly impact your projects. So let’s get deeper and see how to get the best out of this functionality.
The first thing you should remember is that QuerySet Filter enables you to use precise and diverse criteria for filtering data. You can utilize various operators and filters like "equals to", "greater than", "less than", and many other possible options to achieve comprehensive control over the data extracted from the database.
To use these filters, you should become familiar with the concept of QuerySet in Django. QuerySet, in fact, is a representation of queries that are sent to the database and returns the data. Filtering on these QuerySets can be done using various functions like filter(), exclude(), get(), and so on.
A simple example of using filters in Django would be if we want to retrieve all users whose names start with "A". This case is quite easy and quick using the QuerySet Filter and has the advantage of being both faster and allows more research options.
Now, let’s explore a real-life example to better understand how this capability is used in a real project. Assume we have a model named Book and we want to find books that have more than 200 pages. For this, we can use the following command:
books = Book.objects.filter(pages__gt=200)
How does this command work? Let’s go step by step:
books = → we define a variable named books that will hold the result of the filter.
Book.objects → this part allows us to access all model attributes of Book.
filter(pages__gt=200) → using this filter, we can select books that have more than 200 pages. pages__gt=200 means the number of pages is greater than 200.
In this way, we can easily filter data using QuerySet Filters and obtain delightful results.