A Q() object encapsulates a SQL expression in a Python object that can be used in database-related operations.
In general, Q() objects make it possible to define and reuse conditions. This permits the construction of complex database queries using | (OR) and & (AND) operators; in particular, it is not otherwise possible to use OR in QuerySets.
Complex lookups with Q objects
Keyword argument queries – in filter(), etc. – are “AND”ed together. If you need to execute more complex queries (for example, queries with OR statements), you can use Q objects.
A Q object (django.db.models.Q) is an object used to encapsulate a collection of keyword arguments. These keyword arguments are specified as in “Field lookups” above.
For example, this Q object encapsulates a single LIKE query:
from django.db.models import Q
Q(question__startswith='What')
Q objects can be combined using the & and | operators. When an operator is used on two Q objects, it yields a new Q object.
For example, this statement yields a single Q object that represents the “OR” of two "question__startswith" queries:
Q(question__startswith='Who') | Q(question__startswith='What')
This is equivalent to the following SQL WHERE clause:
WHERE question LIKE 'Who%' OR question LIKE 'What%'
You can compose statements of arbitrary complexity by combining Q objects with the & and | operators and use parenthetical grouping. Also, Q objects can be negated using the ~ operator, allowing for combined lookups that combine both a normal query and a negated (NOT) query:
Q(question__startswith='Who') | ~Q(pub_date__year=2005)
Each lookup function that takes keyword-arguments (e.g. filter(), exclude(), get()) can also be passed one or more Q objects as positional (not-named) arguments. If you provide multiple Q object arguments to a lookup function, the arguments will be “AND”ed together. For example:
Poll.objects.get(
Q(question__startswith='Who'),
Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6))
)
... roughly translates into the SQL:
SELECT * from polls WHERE question LIKE 'Who%'
AND (pub_date = '2005-05-02' OR pub_date = '2005-05-06')
Lookup functions can mix the use of Q objects and keyword arguments. All arguments provided to a lookup function (be they keyword arguments or Q objects) are “AND”ed together. However, if a Q object is provided, it must precede the definition of any keyword arguments. For example:
Poll.objects.get(
Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)),
question__startswith='Who')
... would be a valid query, equivalent to the previous example; but:
# INVALID QUERY
Poll.objects.get(
question__startswith='Who',
Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)))
... would not be valid.