Django运行SQL语句

1、Manager.raw(raw_query, params=None, translations=None)

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

这个方法接受一个原始的SQL查询，执行它，并返回一个django.db.models.query。RawQuerySet实例。这个RawQuerySet实例可以像普通的QuerySet一样遍历，以提供对象实例。

（1）字段匹配

>>> Person.objects.raw('''SELECT first AS first_name,
...                              last AS last_name,
...                              bd AS birth_date,
...                              pk AS id,
...                       FROM some_other_table''')

>>> name_map = {'first': 'first_name', 'last': 'last_name', 'bd': 'birth_date', 'pk': 'id'}
>>> Person.objects.raw('SELECT * FROM some_other_table', translations=name_map)

（2）即使没有显示表明查询字段，也可以获取

>>> for p in Person.objects.raw('SELECT id, first_name FROM myapp_person'):
...     print(p.first_name, # This will be retrieved by the original query
...           p.last_name) # This will be retrieved on demand
...
John Smith
Jane Jones

（3）执行带参数SQL

字符串用%s占位符

字典用%(key)s占位符

>>> lname = 'Doe'
>>> Person.objects.raw('SELECT * FROM myapp_person WHERE last_name = %s', [lname])

（4）严禁使用字符串拼接

>>> query = 'SELECT * FROM myapp_person WHERE last_name = %s' % lname
>>> Person.objects.raw(query)

（4）参数不能用引号包裹

>>> query = "SELECT * FROM myapp_person WHERE last_name = '%s'"

2、通过connection.cursor()执行SQL

对象django.db.connection表示默认的数据库连接。要使用数据库连接，请调用connection.cursor()来获得一个游标对象。然后调用cursor.execute(sql， [params])方法以执行sql

cursor.fetchone()或cursor.fetchall()以返回结果行。

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

（1）传递百分比参数需要写两个百分号

cursor.execute("SELECT foo FROM bar WHERE baz = '30%%' AND id = %s", [self.id])

（2）cursor执行不会返回列名

用字典或命名元组

def dictfetchall(cursor):
    "Return all rows from a cursor as a dict"
    columns = [col[0] for col in cursor.description]
    return [
        dict(zip(columns, row))
        for row in cursor.fetchall()
    ]

from collections import namedtuple

def namedtuplefetchall(cursor):
    "Return all rows from a cursor as a namedtuple"
    desc = cursor.description
    nt_result = namedtuple('Result', [col[0] for col in desc])
    return [nt_result(*row) for row in cursor.fetchall()]

>>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2");
>>> dictfetchall(cursor)
[{'parent_id': None, 'id': 54360982}, {'parent_id': None, 'id': 54360880}]