django 执行原始SQL

作者: BeginMan
发布时间:2015-07-29 11:35:08

一、参考文档和资料

Django 1.2

https://docs.djangoproject.com/en/1.2/topics/db/sql/

二、知识点总结

Django提供两种方式执行(performing)原始的SQL查询:

(1)Manager.raw():执行原始查询并返回模型实例

(2)Executing custom SQL directly:直接执行自定义SQL,这种方式可以完全避免数据模型,而是直接执行原始的SQL语句。

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

这种方法通过执行原始的SQL查询并返回一个RawQuerySet实例。返回的RawQuerySet实例就如QuerySet一样能够迭代。

>>> from account.models import person            #导入person类
>>> raw_sql = 'select * from Person'             #原始sql语句
>>> raw_querySet = person.objects.raw(raw_sql)   #xx.objects.raw()执行原始sql
>>> print raw_querySet
<RawQuerySet: 'select * from Person'>            #RawQuerySet对象
>>> for obj in raw_querySet:                     #迭代循环
...     print obj
...
张三
李四
王五

 

 注意,原始SQL里的model,如果在db_table 没有定义,则使用app的名称,后面下划线 后面接模型类的名称,如"Myblog_New";上面的例子,在定义类的时候已经这样处理了:

Class New(models.Model):
    ......
    ......
#自定义表名
    class Meta:
        db_table = 'New'

 2、查询字段映射到模型字段(Mapping query fields to model fields)

raw() 方法自动通过查询字段映射到 model字段,并且是通过名称来匹配,这意味着我们可以使用SQL子句(clause)

注意当输入查询字段的时候,不要漏了主键(id),否则会出错:InvalidQuery: Raw query must include the primary key

(1)、当有其他表(如表1)的时候,如果sql查询中对应名字(xx as yy)与表2中的字段匹配的话(yy)则model实例将会被创建:

>>> table1.objects.raw('''SELECT first AS first_name,
...                              last AS last_name,
...                              bd AS birth_date,
...                              pk as id,
...                       FROM some_other_table''')

(2)、可以使用raw()方法中的translations参数进行query 字段到model字段的映射。

>>> name_map = {'first': 'first_name', 'last': 'last_name', 'bd': 'birth_date', 'pk': 'id'}
>>> table1.objects.raw('SELECT * FROM some_other_table', translations=name_map)

some_other_table 字段(first,last,bd,pk) 通过字典映射table1字段(first_name,last_name,birth_date,id)

3、索引查找(Index lookups)

first_person = Person.objects.raw('SELECT * from myapp_person')[0]
first_person = Person.objects.raw('SELECT * from myapp_person LIMIT 1')[0]
#然而,索引和切片不是在数据库级别上执行(除LIMIT外)

4、延迟模型字段(Deferring model fields)

Fields may also be left out(left out:忽视,不考虑;被遗忘),这意味着该字段的查询将会被排除在根据需要时的加载。

>>> for p in Person.objects.raw('SELECT id, first_name FROM myapp_person'):
...     print p.first_name, # 这将检索到原始查询
...     print p.last_name # 这将检索需求
...
John Smith
Jane Jones

 

5、传递参数(Passing parameters into raw())

如果需要执行参数化查询,您可以使用params参数原始()

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

注意,参数必须是一系列列表类型的。

不能在raw()方法中使用格式化字符串:

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

 

 四、直接执行自定义SQL

Manager.raw()远远不够,可直接执行自定义SQL,直接执行UPDATE, INSERT, DELETE,而这些都是manager.raw()不能实现的。所以要直接执行自定义SQL

操作流程如下:

导入 form django.db import connection,transaction

django.db.connection:代表默认的数据库连接
django.db.transaction:代表默认数据库事务(transaction)
connection.cursor(): 获得一个游标(cursor)对象
cursor.execute(sql, [params]):执行SQL
cursor.fetchone() 或者 cursor.fetchall():返回结果行

如果执行修改操作,则调用transaction.commit_unless_managed()来保证你的更改提交到数据库。

 实例如下:

def sql(request):
    """
    ----------------------------------------------
    Function:    执行原始的SQL
    DateTime:    2013/x/xx
    ----------------------------------------------
    """
    from django.db import connection,transaction
    cursor = connection.cursor()            #获得一个游标(cursor)对象
    #更新操作
    cursor.execute('update other_other2 set name ="李四" where id=%s',[3])    #执行sql语句
    transaction.commit_unless_managed()     #提交到数据库
    #查询操作
    cursor.execute('select * from other_other2 where id>%s' ,[1])
    raw = cursor.fetchone()                 #返回结果行 或使用 #raw = cursor.fetchall()
    
    #如果连接多个数据库则使用django.db.connections
    from django.db import connections
    _cursor = connections['other_database'].cursor()
    #如果执行了更新、删除等操作
    transaction.commit_unless_managed(using='other_databases') 
    return render_to_response('other/sql.html',{'raw':raw})

django.db.connections:针对使用多个数据库

from django.db import connections
cursor = connections['my_db_alias'].cursor()
# Your code here...
transaction.commit_unless_managed(using='my_db_alias')

 通常我们不需要手动调用transaction.commit_unless_managed(),我们可以这样做:

调用set_dirty()自动映射到操作的字段

@commit_on_success
def my_custom_sql_view(request, value):
    from django.db import connection, transaction
    cursor = connection.cursor()

    # Data modifying operation
    cursor.execute("UPDATE bar SET foo = 1 WHERE baz = %s", [value])

    # Since we modified data, mark the transaction as dirty
    transaction.set_dirty()

    # Data retrieval operation. This doesn't dirty the transaction,
    # so no call to set_dirty() is required.
    cursor.execute("SELECT foo FROM bar WHERE baz = %s", [value])
    row = cursor.fetchone()

    return render_to_response('template.html', {'row': row})

五、个人常用:

def Message(request,msg_id):
.........
where=msg_id
            sql='''
            select t.id, t.real_name, t2.* from auth_user t join (
            select max(is_red) as is_red,add_user_id,task_id from card 
       where msg_id=%s GROUP BY task_id,add_user_id) t2 ON t2.add_user_id=t.id ''' %where cursor = connection.cursor() cursor.execute(sql) fetchall = cursor.fetchall() card=[] for obj in fetchall: dic={} dic['user_id']=obj[0] dic['real_name']=obj[1] dic['is_red']=obj[2] dic['add_user']=obj[3] dic['task_id']=obj[4] card.append(dic) context['card']=card

 六、整体实例演示

 

#搜索数据
 if request.method == 'POST':
            type = int(request.POST.get('type',0))
            s_title = request.POST.get('s_title')
            if not type:
                type = 'type>0'
            else:
                type = 'type=%s' %type
          
            if s_title:
                s_title = "title LIKE '%%%%%s%%%%'" %s_title
            else:
                s_title = 'id>0'
            sql = u'''
            SELECT @row := @row + 1 as row,t.* FROM(SELECT * FROM version WHERE %s AND %s) t,(SELECT @row := 0) r ORDER BY release_date''' %(type,s_title)
            print sql
            cursor = connection.cursor()
            cursor.execute(sql)
            fetchall = cursor.fetchall()

 

#添加、更新数据
now = datetime.datetime.now()
    if request.method == 'POST':
        id = int(request.POST.get('id',0))  #编辑对应id,如果新添加的则id=0
        version = request.POST.get('no')   
        type = int(request.POST.get('type'))      
        title = request.POST.get('title')                
        content = request.POST.get('content')      
        
        if not id:      #添加
            sql = 'insert into version(type,version,title,content,release_date) values(%s,%s,%s,%s,%s)'
            cursor = connection.cursor()
            cursor.execute(sql,[type,version,title,content,now])
            transaction.commit_unless_managed()
            return HttpResponse('ok')
        else:           #编辑
            sql = 'update version set type=%s,version=%s,title=%s,content=%s where id=%s'
            cursor = connection.cursor()
            cursor.execute(sql,[type,version,title,content,id])
            transaction.commit_unless_managed()
            return HttpResponse('ok')
#异步获取数据
...
 if request.method == 'POST':
        id = int(request.POST.get('id',0)) 
        cursor = connection.cursor()
        cursor.execute('select * from version where id =%s',[id])
        raw = cursor.fetchone()
        lis =[]
        dic = {}
        dic['type'] =raw[1]
        dic['version']=raw[2]
        dic['title'] = raw[3]
        dic['content'] = raw[4]
        lis.append(dic)
        return ajax.ajax_ok(lis) 
#删除数据
 if request.method == 'POST':
        id = int(request.POST.get('id',0)) 
        cursor = connection.cursor()
        cursor.execute('delete from version where id=%s',[id])  
        transaction.commit_unless_managed()
        return HttpResponse('ok')  

 

标签: Django Go SQL
来源:http://www.cnblogs.com/BeginMan/archive/2013/05/27/3101322.h

推荐: