显示ORM底层生成SQL

def showsql():
		from django.db import connection
		queries = connection.queries
		print queries[-1]['sql']

查询单个对象

#所有的继承自models.Model的类 都会有一个叫objects（管理器）

* 查询一个  （有且只能有一个）（少于一个或者多余一个都报错）
			* 返回值Movie对象
	
			Movie.objects.get(mid=147)
			
			SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE `movie`.`mid` = 147

* 获得第一个

			Movie.objects.first()	

			SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` ORDER BY `movie`.`mid` ASC LIMIT 1
* 获得最后一个

			Movie.objects.last()

			SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` ORDER BY `movie`.`mid` DESC LIMIT 1
* 获得记录的总数

			Movie.objects.count()

			SELECT COUNT(*) AS `__count` FROM `movie`

查询多个对象

* 获得所有的记录

			Movie.objects.all()
			# 在diango的1.11.6中默认只是获得21个，
			# 懒加载
			SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM 			`movie` LIMIT 21
* 切片 （不支持负数索引）
		Movie.objects.all()[20:40]
		# 底层直接使用了limit字句，可以自动的分页
		# django的orm性能非常强大，能节省很多工作		
		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` 		LIMIT 20 OFFSET 20
* 过滤
		#  集和（游标，结果集，查询集）
		Movie.objects.filter(mname='麻辣学院')

		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE `movie`.`mname` = '麻辣学院' LIMIT 21
	
* 模糊查询 
	* like
	* %(多个字符) _(一个字符)
	* SELECT * from movie WHERE mname LIKE '%爱情_'
* 查询爱情结尾的

			SELECT * from movie WHERE mname LIKE '%爱情'

			Movie.objects.filter(mname__endswith='爱情')

			SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM 			`movie` WHERE `movie`.`mname` LIKE BINARY '%爱情' LIMIT 21
* 查询爱情开头的

			SELECT * from movie WHERE mname LIKE '爱情%'
			
			Movie.objects.filter(mname__startswith='爱情')
			
			SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM 			`movie` WHERE `movie`.`mname` LIKE BINARY '爱情%' LIMIT 21
* 包含爱情的

		SELECT * from movie where mname like '%爱情%'

		Movie.objects.filter(mname__contains='爱情')


		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` 		WHERE `movie`.`mname` LIKE BINARY '%爱情%' LIMIT 21
* 完全相等

		Movie.objects.filter(mname__exact='麻辣学院')
		Movie.objects.filter(mname='麻辣学院')
	
		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` 		WHERE `movie`.`mname` = '麻辣学院' LIMIT 21
* 忽略大小写

		Movie.objects.filter(mname__istartswith='h')
Movie.objects.filter(mname__icontains='h')

* 查询某个字段是否为null

		Movie.objects.filter(mname__isnull=True)


* 多条件查询

		Movie.objects.filter(mname__contains='爱情',mid=147)
		
			and

			
		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE (`movie`.`mname` LIKE BINARY '%爱情%' AND `movie`.`mid` = 147) LIMIT 21

		Movie.objects.filter(mname__contains='爱情').filter(mid=147)

* 部分查询

		Movie.objects.values('mname','mid').filter(mname__contains='爱情')
		
* 排除一部分

	Movie.objects.filter(mname__contains='爱情').exclude(mname__startswith='爱情')

		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` 		WHERE (`movie`.`mname` LIKE BINARY '%爱情%' AND NOT (`movie`.`mname` LIKE BINARY '爱情%')) LIMIT 21

* 排序

		Movie.objects.order_by('mid')
	
		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` 		ORDER BY `movie`.`mid` ASC LIMIT 21


		Movie.objects.order_by('-mid')

		SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` 		ORDER BY `movie`.`mid` DESC LIMIT 21

日期查询

* 查询大于某个时间的记录

		Post.objects.filter(created__gt='2017-10-20')
 
		SELECT `post_post`.`id`, `post_post`.`title`, `post_post`.`created` FROM `post_post` WHERE 			`post_post`.`created` > '2017-10-20' LIMIT 21
 * 查询最近一个月的帖子（查询最近不活跃的用户）
 
		def get_recent_month_posts():
		    import datetime
		    current = datetime.date.today()-datetime.timedelta(days=30)
		    current = str(current)
		    return Post.objects.filter(created__gt=current)
		    
 * 查询十月二十号--十一月二十号的所有的记录
   * 错误的

			Post.objects.filter(created__in=('2017-10-20','2017-11-20'))
			指的是这两个时间中的一个
  
  * 正确 （sql语句）

		Post.objects.filter(created__range=('2017-10-20','2017-11-20'))

				
		SELECT `post_post`.`id`, `post_post`.`title`, `post_post`.`created` FROM `post_post` WHERE 			`post_post`.`created` BETWEEN '2017-10-20' AND '2017-11-20' LIMIT 21

增加

#方法1

	post = Post(title='博客11',created='2017-2-28')
	post.save()

#方法2

	Post.objects.create(title='博客12',created='2018-11-11')
	返回值是添加的对象

删除

#方法1
	Movie.objects.get(mid='147').delete()
    
    
    #BINARY不是函数，是类型转换运算符,比较时 区分大小写
    DELETE FROM `movie` WHERE `movie`.`mname` LIKE BINARY 'h%'

* 方法2 (删除所有包含博客名字的帖子)

    Post.objects.filter(title__contains='博客').delete()

修改

#方法1  （更新的是所有的字段）
	
	
	post = Post.objects.first()
	post.title='更新了'
	post.save()
			 	
	UPDATE `post_post` SET `title` = '更新了', `created` = '2017-11-27' WHERE `post_post`.`id` = 26
  	
#方法2（只更新修改的字段），推荐使用

	Post.objects.filter(id=26).update(title='又更新了')

	UPDATE `post_post` SET `title` = '又更新了' WHERE `post_post`.`id` = 26

over......