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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