Coologic介绍
django模型的objects对象中有filter、get等方法，其中可以“字段=XXX”的方式填入参数，最终构成AND关系的SQL Where子句，若需要OR或多种混合的复杂搜索需要使用Q对象。
除此以为，django还支持利用“__”方式实现查找条件关键字、__方式的多表连接查询。
查找关键字
__exact 精确等于 like ‘aaa’ __iexact 精确等于 忽略大小写 ilike ‘aaa’ __contains 包含 like ‘%aaa%’ __icontains 包含 忽略大小写 ilike ‘%aaa%’，但是对于sqlite来说，contains的作用效果等同于icontains。 __gt 大于 __gte 大于等于 __lt 小于 __lte 小于等于 __in 存在于一个list范围内 __startswith 以…开头 __istartswith 以…开头 忽略大小写 __endswith 以…结尾 __iendswith 以…结尾，忽略大小写 __range 在…范围内 __year 日期字段的年份 __month 日期字段的月份 __day 日期字段的日 __isnull=True/False
范例：filter(name__contains=’techie’)等效于WHERE name like ‘%techie%’
连表查询
class A(models.Model):
name = models.CharField()
class B(models.Model):
aa = models.ForeignKey(A)
B.objects.filter(aa__name__contains='test')通过B的外键找到A中name字段包含test内容的数据
class A(models.Model):
name = models.CharField()
class B(models.Model):
aa = models.ForeignKey(A,related_name="FAN")
bb = models.CharField()
A.objects.filter(FAN__bb='XXXX')反向查询，查询出所有(B.aa=A且B.bb=XXXX)的A实例
Q对象使用
官方文档：https://docs.djangoproject.com/en/2.0/topics/db/queries/#complex-lookups-with-q-objects
引用django.db.models.Q
Q对象与SQL语句对应关系如下：
Q(question='Who') | Q(question='What') WHERE question = 'Who' OR question = 'What'
Model.objects.get(
Q(question='Who'),
Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6))
)
SELECT * from model WHERE question = 'Who' AND (pub_date = '2005-05-02' OR pub_date = '2005-05-06')
如果有比较复杂的关系，可以像使用容器一样构造Q对象：
单一类型条件查询：
q1 = Q()
q1.connector = 'OR'
q1.children.append(('id', 1))
q1.children.append(('id', 2))
q1.children.append(('id', 3))
models.Tb1.objects.filter(q1)符合类型条件查询：
con = Q()
q1 = Q()
q1.connector = 'OR'
q1.children.append(('id', 1))
q1.children.append(('id', 2))
q1.children.append(('id', 3))
q2 = Q()
q2.connector = 'OR'
q2.children.append(('status', '在线'))
con.add(q1, 'AND')
con.add(q2, 'AND')
models.Tb1.objects.filter(con)Q对象官方使用范例
https://github.com/django/django/blob/master/tests/or_lookups/tests.py
from datetime import datetime
from operator import attrgetter
from django.db.models import Q
from django.test import TestCase
from .models import Article
class OrLookupsTests(TestCase):
def setUp(self):
self.a1 = Article.objects.create(
headline='Hello', pub_date=datetime(2005, 11, 27)
).pk
self.a2 = Article.objects.create(
headline='Goodbye', pub_date=datetime(2005, 11, 28)
).pk
self.a3 = Article.objects.create(
headline='Hello and goodbye', pub_date=datetime(2005, 11, 29)
).pk
def test_filter_or(self):
self.assertQuerysetEqual(
(
Article.objects.filter(headline__startswith='Hello') |
Article.objects.filter(headline__startswith='Goodbye')
), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline")
)
self.assertQuerysetEqual(
Article.objects.filter(headline__contains='Hello') | Article.objects.filter(headline__contains='bye'), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline")
)
self.assertQuerysetEqual(
Article.objects.filter(headline__iexact='Hello') | Article.objects.filter(headline__contains='ood'), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline")
)
self.assertQuerysetEqual(
Article.objects.filter(Q(headline__startswith='Hello') | Q(headline__startswith='Goodbye')), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline")
)
def test_stages(self):
# You can shorten this syntax with code like the following, which is
# especially useful if building the query in stages:
articles = Article.objects.all()
self.assertQuerysetEqual(
articles.filter(headline__startswith='Hello') & articles.filter(headline__startswith='Goodbye'),
[]
)
self.assertQuerysetEqual(
articles.filter(headline__startswith='Hello') & articles.filter(headline__contains='bye'), [
'Hello and goodbye'
],
attrgetter("headline")
)
def test_pk_q(self):
self.assertQuerysetEqual(
Article.objects.filter(Q(pk=self.a1) | Q(pk=self.a2)), [
'Hello',
'Goodbye'
],
attrgetter("headline")
)
self.assertQuerysetEqual(
Article.objects.filter(Q(pk=self.a1) | Q(pk=self.a2) | Q(pk=self.a3)), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline"),
)
def test_pk_in(self):
self.assertQuerysetEqual(
Article.objects.filter(pk__in=[self.a1, self.a2, self.a3]), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline"),
)
self.assertQuerysetEqual(
Article.objects.filter(pk__in=(self.a1, self.a2, self.a3)), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline"),
)
self.assertQuerysetEqual(
Article.objects.filter(pk__in=[self.a1, self.a2, self.a3, 40000]), [
'Hello',
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline"),
)
def test_q_repr(self):
or_expr = Q(baz=Article(headline="Fo?"))
self.assertEqual(repr(or_expr), "<Q: (AND: ('baz', <Article: Fo?>))>")
negated_or = ~Q(baz=Article(headline="Fo?"))
self.assertEqual(repr(negated_or), "<Q: (NOT (AND: ('baz', <Article: Fo?>)))>")
def test_q_negated(self):
# Q objects can be negated
self.assertQuerysetEqual(
Article.objects.filter(Q(pk=self.a1) | ~Q(pk=self.a2)), [
'Hello',
'Hello and goodbye'
],
attrgetter("headline")
)
self.assertQuerysetEqual(
Article.objects.filter(~Q(pk=self.a1) & ~Q(pk=self.a2)), [
'Hello and goodbye'
],
attrgetter("headline"),
)
# This allows for more complex queries than filter() and exclude()
# alone would allow
self.assertQuerysetEqual(
Article.objects.filter(Q(pk=self.a1) & (~Q(pk=self.a2) | Q(pk=self.a3))), [
'Hello'
],
attrgetter("headline"),
)
def test_complex_filter(self):
# The 'complex_filter' method supports framework features such as
# 'limit_choices_to' which normally take a single dictionary of lookup
# arguments but need to support arbitrary queries via Q objects too.
self.assertQuerysetEqual(
Article.objects.complex_filter({'pk': self.a1}), [
'Hello'
],
attrgetter("headline"),
)
self.assertQuerysetEqual(
Article.objects.complex_filter(Q(pk=self.a1) | Q(pk=self.a2)), [
'Hello',
'Goodbye'
],
attrgetter("headline"),
)
def test_empty_in(self):
# Passing "in" an empty list returns no results ...
self.assertQuerysetEqual(
Article.objects.filter(pk__in=[]),
[]
)
# ... but can return results if we OR it with another query.
self.assertQuerysetEqual(
Article.objects.filter(Q(pk__in=[]) | Q(headline__icontains='goodbye')), [
'Goodbye',
'Hello and goodbye'
],
attrgetter("headline"),
)
def test_q_and(self):
# Q arg objects are ANDed
self.assertQuerysetEqual(
Article.objects.filter(Q(headline__startswith='Hello'), Q(headline__contains='bye')), [
'Hello and goodbye'
],
attrgetter("headline")
)
# Q arg AND order is irrelevant
self.assertQuerysetEqual(
Article.objects.filter(Q(headline__contains='bye'), headline__startswith='Hello'), [
'Hello and goodbye'
],
attrgetter("headline"),
)
self.assertQuerysetEqual(
Article.objects.filter(Q(headline__startswith='Hello') & Q(headline__startswith='Goodbye')),
[]
)
def test_q_exclude(self):
self.assertQuerysetEqual(
Article.objects.exclude(Q(headline__startswith='Hello')), [
'Goodbye'
],
attrgetter("headline")
)
def test_other_arg_queries(self):
# Try some arg queries with operations other than filter.
self.assertEqual(
Article.objects.get(Q(headline__startswith='Hello'), Q(headline__contains='bye')).headline,
'Hello and goodbye'
)
self.assertEqual(
Article.objects.filter(Q(headline__startswith='Hello') | Q(headline__contains='bye')).count(),
3
)
self.assertSequenceEqual(
Article.objects.filter(Q(headline__startswith='Hello'), Q(headline__contains='bye')).values(), [
{"headline": "Hello and goodbye", "id": self.a3, "pub_date": datetime(2005, 11, 29)},
],
)
self.assertEqual(
Article.objects.filter(Q(headline__startswith='Hello')).in_bulk([self.a1, self.a2]),
{self.a1: Article.objects.get(pk=self.a1)}
)
F对象使用
官方文档：https://docs.djangoproject.com/en/2.0/ref/models/expressions/#f-expressions
有关聚合、分组、F查询可看博客：django-聚合、分组、F查询和Q查询、总结
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