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This article introduces the relevant knowledge of "what is the role of select_related in dajngo ORM query". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

We analyze the role of select_related based on the following model.

There are two query methods:

a. Without select_related

Book = Book.objects.filter (pk=1) # query database 1

N = book.name # needs to query database 2

A = book.age # needs to query database 3

* A total of three queries were initiated to the database.

b. With select_related

Book = Book.objects.select_related () .filter (pk=1) # needs to query database 1

N = book.name # directly from the book object

A = book.age # directly from the book object

* A total of one query was initiated to the database.

In other words, using the select_related () method to query all the objects associated with Book and put them into the object at one time, there is no need to connect to the database when querying again, which saves the times and time of querying the database later.

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