Django基础07篇 ORM操作

1.新增（类似数据库操作的insert）

# 新增
#方式一：
models.Category.objects.create(name='MySQL')
#方式二：
c = models.Category(name='Oracle')
c.save()
 
models.Article.objects.create(
    title='orm学习',
    content='orm学习, content',
    category_id=2
)  # 知道外键，id
 
category = models.Category.objects.get(id=3)
models.Article.objects.create(
    title='orm学习2',
    content='orm学习2, content',
    category=category
    # category_id=category.id     #  category=category  这两行是等价的
)  # 不知道外键，id

2.修改（类似数据库操作的update）

# 修改
 
c = models.Category.objects.get(id=3)
c.name = 'JAVA'
c.save()  # 修改单条数据
 
models.Category.objects.all().update(name='abc')  # 修改全表的某个字段
 
# 按照某个条件修改
models.Category.objects.filter(name='abc').update(name='ccc', age=15)

3.删除（类似数据库操作的delete）

# 删除
c = models.Category.objects.get(id=6)
c.delete()  # 删除某一条
 
models.Category.objects.all().delete()  # 删除全表数据
 
# 按照某些条件删除
models.Category.objects.filter(name='abc').delete()

4.查询（类似数据库操作的select） 

# 简单查询
result = models.Category.objects.all() # 查询所有的数据
print(result)
print(result.values())
print(result.values_list())
print(result.values('name'))  # 根据某个字段的值过滤结果集
print(result.values_list('name'))  # 根据某个字段的值过滤结果集
print(result.first())  # 获取结果集的第一个元素
print(result.count())  # 获取结果集中结果个数
result = models.Category.objects.get(id=1)  # 获取单条结果
print(result)
# 复杂查询
# 大于、小于、大于等于、小于等于、in 、not 、或
 
result = models.Article.objects.filter(read_count__gt=0)  # 大于0
print(result)
result = models.Article.objects.filter(read_count__gte=0)  # 大于等于0
print(result)
result = models.Article.objects.filter(read_count__lt=0)  # 小于0
print(result)
result = models.Article.objects.filter(read_count__lte=0)  # 小于等于0
print(result)
result = models.Article.objects.exclude(read_count=0)  # 不等于  not
print(result)
result = models.Article.objects.filter(id__in=[1, 2, 3])  # in
print(result)
# 模糊查询
result = models.Article.objects.filter(title__contains='orm')  # like，包含某个字符串
print(result)
result = models.Article.objects.filter(title__icontains='orm')  # like，忽略大小写包含某个字符串
print(result)
result = models.Article.objects.filter(title__endswith='xxx')  # 以什么结尾
 
# 如果用get取单独1条数据时有报错风险，建议使用下面的代码，更健壮
query_set = models.Article.objects.filter(id=5)
if query_set:
    article = query_set.first()
else:
    print('这条数据不存在')
 
# 多条件查询 or  and
# where read_count >0 or title like '%orm%'
result = models.Article.objects.filter(Q(read_count__gt=0) | Q(title__contains='orm'))
print(result)
# where read_count >0 and title like '%orm%'
result = models.Article.objects.filter(Q(read_count__gt=0) & Q(title__contains='orm'))
print(result)
result = models.Article.objects.filter(read_count=0,title='python06篇')
print(result)
# where read_count >0 and title not like '%orm%'
result = models.Article.objects.filter(Q(read_count=0) & ~Q(title__contains='orm'))  # ~放在Q()前代表Q的非
print(result)

查询结果

<QuerySet [<Category: python>, <Category: Linux>, <Category: JAVA>, <Category: apche>, <Category: MySQL>]>
<QuerySet [{'id': 1, 'create_time': datetime.datetime(2020, 11, 18, 23, 5, 22, 413832), 'update_time': datetime.datetime(2020, 11, 18, 23, 5, 22, 413832), 'name': 'python'}, {'id': 2, 'create_time': datetime.datetime(2020, 11, 18, 23, 6, 14, 86852), 'update_time': datetime.datetime(2020, 11, 18, 23, 6, 14, 86852), 'name': 'Linux'}, {'id': 3, 'create_time': datetime.datetime(2020, 11, 18, 23, 6, 21, 743606), 'update_time': datetime.datetime(2020, 11, 29, 15, 12, 4, 149925), 'name': 'JAVA'}, {'id': 4, 'create_time': datetime.datetime(2020, 11, 18, 23, 33, 40, 410426), 'update_time': datetime.datetime(2020, 11, 18, 23, 33, 40, 410426), 'name': 'apche'}, {'id': 5, 'create_time': datetime.datetime(2020, 11, 29, 14, 59, 9, 537770), 'update_time': datetime.datetime(2020, 11, 29, 14, 59, 9, 537770), 'name': 'MySQL'}]>
<QuerySet [(1, datetime.datetime(2020, 11, 18, 23, 5, 22, 413832), datetime.datetime(2020, 11, 18, 23, 5, 22, 413832), 'python'), (2, datetime.datetime(2020, 11, 18, 23, 6, 14, 86852), datetime.datetime(2020, 11, 18, 23, 6, 14, 86852), 'Linux'), (3, datetime.datetime(2020, 11, 18, 23, 6, 21, 743606), datetime.datetime(2020, 11, 29, 15, 12, 4, 149925), 'JAVA'), (4, datetime.datetime(2020, 11, 18, 23, 33, 40, 410426), datetime.datetime(2020, 11, 18, 23, 33, 40, 410426), 'apche'), (5, datetime.datetime(2020, 11, 29, 14, 59, 9, 537770), datetime.datetime(2020, 11, 29, 14, 59, 9, 537770), 'MySQL')]>
<QuerySet [{'name': 'python'}, {'name': 'Linux'}, {'name': 'JAVA'}, {'name': 'apche'}, {'name': 'MySQL'}]>
<QuerySet [('python',), ('Linux',), ('JAVA',), ('apche',), ('MySQL',)]>
python
5
python
<QuerySet [<Article: orm学习2>, <Article: python基础篇03>, <Article: python基础篇01>]>
<QuerySet [<Article: orm学习2>, <Article: orm学习>, <Article: python08篇>, <Article: python07篇>, <Article: python06篇>, <Article: python05篇>, <Article: python04篇>, <Article: python基础篇03>, <Article: python基础篇02>, <Article: python基础篇01>]>
<QuerySet []>
<QuerySet [<Article: orm学习>, <Article: python08篇>, <Article: python07篇>, <Article: python06篇>, <Article: python05篇>, <Article: python04篇>, <Article: python基础篇02>]>
<QuerySet [<Article: orm学习2>, <Article: python基础篇03>, <Article: python基础篇01>]>
<QuerySet [<Article: python基础篇03>, <Article: python基础篇02>, <Article: python基础篇01>]>
<QuerySet [<Article: orm学习2>, <Article: orm学习>]>
<QuerySet [<Article: orm学习2>, <Article: orm学习>]>
<QuerySet [<Article: orm学习2>, <Article: orm学习>, <Article: python基础篇03>, <Article: python基础篇01>]>
<QuerySet [<Article: orm学习2>]>
<QuerySet [<Article: python06篇>]>
<QuerySet [<Article: python08篇>, <Article: python07篇>, <Article: python06篇>, <Article: python05篇>, <Article: python04篇>, <Article: python基础篇02>]>