ORM
- 对象关系映射(Object relational mapping)
- 实现实体(数据模型)和数据库的解耦
- 将sql语句的操作转换成对对象的操作
切换mysql数据库
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先创建数据库
create database models charset=utf8
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在settings中
DATABASES = { 'default': { 'ENGINE': 'django.db.backends.mysql', 'NAME': "models", 'USER':'root', 'PASSWORD':'admin', 'HOST':'127.0.0.1', 'PORT':3306 } }
查看执行的sql语句
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connection.queries 指的是执行过的所有的语句,最后一条也就是我们刚刚执行的语句
def showsql(): from django.db import connection queries = connection.queries print queries[-1]['sql']
根据已有的数据库生成model(数据模型)
python manage.py inspectdb > 模块/models.py
Django的ORM类库很有可能会有惰性加载或者懒加载
CURD
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retrieve(检索)
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Movie.objects.all()获得所有的数据
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` LIMIT 21
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get()方法
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Movie.objects.get(mid = 1000)
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE `movie`.`mid` = 1000
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Movie.objects.get(mid__exact =1000 )
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没有数据(DoesNotExist)或者大于1个数据都会出错(MultipleObjectsReturned)
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filter()过滤条件
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Movie.objects.filter(mid__gt=1000)
SELECT
movie
.mid
,movie
.mname
,movie
.mdesc
,movie
.mimg
,movie
.mlink
FROMmovie
WHEREmovie
.mid
> 1000 LIMIT 21 -
Movie.objects.filter(mid__lt=1000)
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE `movie`.`mid` < 1000 LIMIT 21
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Movie.objects.filter(mid__lte=1000)
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Movie.objects.filter(mid__gte=1000)
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Movie.objects.filter(mid__range=(1,1000))
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE `movie`.`mid` BETWEEN 1 AND 1000 LIMIT 21
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Movie.objects.filter(mname__contains=‘爱情’)
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE `movie`.`mname` = '%爱情%' LIMIT 21
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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
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遇到了脏数据(数据清洗)
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name多行文本,有很多空格,换行符
for m in Movie.objects.all(): m.mname=m.mname.strip() m.save()
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查询(爱情开头,了结尾)
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Movie.objects.filter(mname__startswith=‘爱情’,mname__endswith=‘了’)
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Movie.objects.filter(mname__startswith=‘爱情’).filter(mname__endswith=‘了’)
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE (`movie`.`mname` LIKE BINARY '爱情%' AND `movie`.`mname` LIKE BINARY '%了') LIMIT 21
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时间相关的
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User.objects.filter(birthday__in=(‘2000-11-20’,‘2017-11-11’))
SELECT `movie_user`.`id`, `movie_user`.`name`, `movie_user`.`birthday` FROM `movie_user` WHERE `movie_user`.`birthday` IN ('2017-11-11', '2000-11-20') LIMIT 21
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查询最近活跃的用户(F(函数))
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查询的电影不包含爱情的
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Movie.objects.exclude(mname__contains=‘爱情’)
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` WHERE NOT (`movie`.`mname` LIKE BINARY '%爱情%') LIMIT 21
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获得第一条数据
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Movie.objects.first()
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` ORDER BY `movie`.`mid` ASC LIMIT 1
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获得最后一条语句
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Movie.objects.last()
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` ORDER BY `movie`.`mid` DESC LIMIT 1
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惰性查询
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再查询多条数据的时候,什么时候用什么时候查
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movies = Movie.objects.all()
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这时候,有没有查询数据,没有
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什么时候用什么时候查询
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print movies
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多余超过一个数据,会惰性查询
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一个数据get,first,last都不会
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再查询多条数据的时候,不用全部查询过来,而是查询有限的个数(21) 1.11.6
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切割 [1,2,3][1:2]
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Movie.objects.all()[:5]
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Movie.objects.all()[10:20]
SELECT `movie`.`mid`, `movie`.`mname`, `movie`.`mdesc`, `movie`.`mimg`, `movie`.`mlink` FROM `movie` LIMIT 10 OFFSET 10
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用途 分页
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Pagnitor