Ordering and Slicing

Slicing

Slicing, like Author.objects.all()[:1], retrieves a QuerySet limited to a specified range.

Remember that slicing on QuerySets, like [:1], is performed at the database level, so it's an efficient way to limit the number of results returned by a query.

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Author.objects.all()[:2]

Returns the first two objects (equivalent to LIMIT 2 in SQL).

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Author.objects.all()[1:3]

Fetches the second and third objects from the table (akin to OFFSET 1 LIMIT 2 in SQL).

Ordering

To sort a QuerySet, use the order_by() method with the attribute name for ordering. Prepend '-' for descending order.

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Author.objects.order_by("first_name")

For ascending order ( SELECT * FROM Author ORDER BY first_name;).

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Author.objects.order_by("-first_name")

For descending order ( SELECT * FROM Author ORDER BY first_name DESC;).

To define multiple ordering criteria in one order_by statement:

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Author.objects.order_by("first_name", "-last_name")

(SELECT * FROM Author ORDER BY first_name ASC, last_name DESC;).