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14. How to use Q objects for complex queries?

In previous chapters we used Q objects for OR and AND and NOT operations. Q objects provides you complete control over the where clause of the query.

If you want to OR your conditions.

>>> from django.db.models import Q
>>> queryset = User.objects.filter(
    Q(first_name__startswith='R') | Q(last_name__startswith='D')
)
>>> queryset
<QuerySet [<User: Ricky>, <User: Ritesh>, <User: Radha>, <User: Raghu>, <User: rishab>]>

If you want to AND your conditions.

>>> queryset = User.objects.filter(
    Q(first_name__startswith='R') & Q(last_name__startswith='D')
)
>>> queryset
<QuerySet [<User: Ricky>, <User: Ritesh>, <User: rishab>]>

If you want to find all users whose first_name starts with ‘R’, but not if the last_name has ‘Z’

>>> queryset = User.objects.filter(
    Q(first_name__startswith='R') & ~Q(last_name__startswith='Z')
)

If you look at the generated query, you would see

SELECT "auth_user"."id",
       "auth_user"."password",
       "auth_user"."last_login",
       "auth_user"."is_superuser",
       "auth_user"."username",
       "auth_user"."first_name",
       "auth_user"."last_name",
       "auth_user"."email",
       "auth_user"."is_staff",
       "auth_user"."is_active",
       "auth_user"."date_joined"
FROM "auth_user"
WHERE ("auth_user"."first_name"::text LIKE R%
       AND NOT ("auth_user"."last_name"::text LIKE Z%))

You can combine the Q objects in more complex ways to generate complex queries.

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