Django运行SQL语句

一时失言乱红尘 2023-10-06 09:08 67阅读 0赞

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

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

>>> 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)

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

（2）即使没有显示表明查询字段，也可以获取

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

>>> 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

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

（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。

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

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

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

（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

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

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}]

来源:[https://www.cnblogs.com/SunQi-Tony/p/9985616.html][https_www.cnblogs.com_SunQi-Tony_p_9985616.html]

[aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg
[https_www.cnblogs.com_SunQi-Tony_p_9985616.html]: https://www.cnblogs.com/SunQi-Tony/p/9985616.html