如何在 Django 视图中执行原始 SQL 查询？

Question

如何在 views.py 中使用原始 SQL 执行以下操作？

from app.models import Picture

def results(request):
    all = Picture.objects.all()
    yes = Picture.objects.filter(vote='yes').count()
    return render_to_response(
        'results.html', 
        {'picture':picture, 'all':all, 'yes': yes}, 
        context_instance=RequestContext(request)
    )

这个结果函数会是什么样子？

Answer 1

>>> from django.db import connection
>>> cursor = connection.cursor()
>>> cursor.execute('''SELECT count(*) FROM people_person''')
1L
>>> row = cursor.fetchone()
>>> print row
(12L,)
>>> Person.objects.all().count()
12

使用 WHERE 子句过滤赞成票：

>>> cursor.execute('''SELECT count(*) FROM people_person WHERE vote = "yes"''')
1L

Answer 2

Django 文档真的非常好。 基本上你有两种选择执行原始 SQL。您可以使用 Manager.raw() 执行返回模型实例的原始查询，也可以避开模型层并直接执行自定义 SQL。

使用raw()管理器：

>>> for p in Person.objects.raw('SELECT * FROM myapp_person'):
...     print p
John Smith
Jane Jones

如果你想直接绕过模型层，你可以使用django.db.connection它代表默认的数据库连接：

def my_custom_sql():
    from django.db import connection, transaction
    cursor = connection.cursor()

    # Data modifying operation - commit required
    cursor.execute("UPDATE bar SET foo = 1 WHERE baz = %s", [self.baz])
    transaction.commit_unless_managed()

    # Data retrieval operation - no commit required
    cursor.execute("SELECT foo FROM bar WHERE baz = %s", [self.baz])
    row = cursor.fetchone()

    return row

Answer 3

如果您使用 PostgreSQL，则可以在一个查询内完成此操作。
如果没有，您可以相应地更改查询并获取结果。

from django.db import connection

def results(request):
    with connection.cursor() as cursor:
        query = """
        SELECT count(*) as all_count, 
        count(*) FILTER(WHERE vote = 'yes') as yes_count
        FROM people_person;
        """
        cursor.execute(query)
        row = cursor.fetchone()
        all_count, yes_count = row

Answer 4

具有特定数据库名称的原始sql：

from django.db import connections
cursor = connections['default'].cursor()
cursor.execute("select * from table_name")
print(cursor.fetchall())

# manually close the cursor if you are done!
cursor.close()

database_name = Any database created by us
table_name = Any table name created by us

Answer 5

你可以试试这个

Picture.objects.raw("SELECT 1 as id ,"\
 "(SELECT  count(*) as yes FROM people_person WHERE vote='yes') as yes ,"\
 "(SELECT  count(*) FROM people_person WHERE vote='no') as no ,"\
 "(SELECT  count(*) FROM people_person WHERE vote='all') as all ")

Answer 6

raw() 方法可用于执行返回模型实例的原始 sql 查询..查看文档

books = Book.objects.raw('SELECT id,name,pages FROM app_books WHERE pages>100')

如果您可能执行未完全映射到模型的查询..
django.db.connection 代表默认数据库连接所以调用
connection.cursor() 使用数据库连接。 查看文档

from django.db import connection
def my_custom_sql(self):
    with connection.cursor() as cursor:
        cursor.execute("UPDATE bar SET foo = 1 WHERE baz = %s", [self.baz])
        cursor.execute("SELECT foo FROM bar WHERE baz = %s", [self.baz])
        row = cursor.fetchone()

    return row

Answer 7

例如，您有如下所示的 Person 模型：

# "store/models.py"

from django.db import models

class Person(models.Model):
    name = models.CharField(max_length=30)

然后，您可以使用 cursor.execute() 运行原始 SQL 查询 并使用 cursor.fetchall() 获取结果，如果没有更多结果，cursor.fetchall() 返回 [] 如下图。 *文档 解释了更多相关信息：

# "store/views.py"

from django.db import connection
from django.http import HttpResponse

def test(request):
    with connection.cursor() as cursor:
        cursor.execute("SELECT * FROM store_person;") # Here

        for row in cursor.fetchall(): # Here
            print(row)

        print(cursor.fetchall()) # []

    return HttpResponse("Test")

控制台上的输出：

(1, 'Tom')
(2, 'David')
(3, 'Lisa')
[]

并且，您还可以使用 cursor.fetchone() 来获取结果，如果没有更多结果，则使用 cursor.fetchone () 返回 None 如下所示：

# "store/views.py"

from django.db import connection
from django.http import HttpResponse

def test(request):
    with connection.cursor() as cursor:
        cursor.execute("SELECT * FROM store_person;") # Here

        print(cursor.fetchone()) # (1, 'Tom')
        print(cursor.fetchone()) # (2, 'David')
        print(cursor.fetchone()) # (3, 'Lisa')
        print(cursor.fetchone()) # None

    return HttpResponse("Test")

控制台输出：

(1, 'Tom')
(2, 'David')
(3, 'Lisa')
None

并且，您还可以使用 transaction 如下所示：

# "store/views.py"

from django.db import transaction
from django.db import connection
from django.http import HttpResponse

@transaction.atomic # Here
def test(request):
    with connection.cursor() as cursor:
        cursor.execute('''SELECT * FROM store_person;''')

        for row in cursor.fetchall():
            print(row)

    return HttpResponse("Test")

或：

# "store/views.py"

from django.db import transaction
from django.db import connection
from django.http import HttpResponse

def test(request):
    with transaction.atomic(): # Here
        with connection.cursor() as cursor:
            cursor.execute('''SELECT * FROM store_person;''')

            for row in cursor.fetchall():
                print(row)

    return HttpResponse("Test")

或：

DATABASES = {
    'default':{
        'ENGINE':'django.db.backends.postgresql',
        'NAME':'postgres',
        'USER':'postgres',
        'PASSWORD':'admin',
        'HOST':'localhost',
        'PORT':'5432',
        'ATOMIC_REQUESTS': True, # Here
    },
}

然后，事务运行根据下面这些 PostgreSQL 日志。 *我使用PostgreSQL和我的答案 解释了如何记录 PostgreSQL 查询：

[21200] LOG:  duration: 0.008 ms  statement: BEGIN
[21200] LOG:  duration: 1.232 ms  statement: SELECT * FROM store_person;
[21200] LOG:  duration: 0.024 ms  statement: COMMIT