模型
创建两个表
创建模型类
from django.db import models
# Create your models here.
class BookInfo(models.Model):
name = models.CharField(max_length=10, unique=True) # 书名
pub_date = models.DateField(null=True) # 发布时间
read_count = models.IntegerField(default=0) # 阅读量
comment_count = models.IntegerField(default=0) # 点击量
is_delete = models.BooleanField(default=False) # 软删除
class Meta:
db_table = "bookinfo" # 修改表的名字
verbose_name = "书籍管理" # admin站点使用的
def __str__(self):
return self.name
class PeopleInfo(models.Model):
# 定义一个有序字典
GENDER_CHOICE = {
(1, "male"),
(2, "female"),
}
name = models.CharField(max_length=10) # 人物名字
gender = models.SmallIntegerField(choices=GENDER_CHOICE, default=1) # 人物性别
description = models.CharField(max_length=100, null=True) # 人物描述
is_delete = models.BooleanField(default=False) # 软删除
book = models.ForeignKey(BookInfo, on_delete=models.CASCADE) # 外键
class Meta:
db_table = "peopleinfo"
def __str__(self):
return self.name
生成迁移文件
python .\manage.py makemigrations
执行迁移文件
python .\manage.py migrate
数据库表名
模型类如果未指明表名,django默认以小写app应用名_小写模型名为数据库表名
可通过db_table指明数据库表名,在模型类里面进行定义
class Meta:
db_table = "bookinfo" # 修改表的名字
verbose_name = "书籍管理" # admin站点使用的
关于主键
django会为表创建自动增长的主键列,每个模型只能有一个主键列,如果使用选项设置某属性为主键列后django不会再创建自动增长的主键列
属性名命名限制
-
不能是python的保留关键字
-
不允许使用连续的下划线,这是由django的查询方式决定的
-
定义属性时需要指定字段类型,通过 字段类型的参数指定选项
属性名=models.字段类型(选项)
字段类型
|----------------------|-----------------------------------------------------------------------|
| 类型 | 说明 |
| AutoField | 自增整数,不指定是django会自动创建,属性名为id |
| BooleanField | 布尔字段,值为True或False |
| NullBooleanField | 支持Null、True、False三种值 |
| CharField | 字符串,参数max_length表示最大字符个数 |
| TextField | 大文本字段,一般超过4000个字符时使用 |
| IntegerField | 整数 |
| DecimaIField | 十进制浮点数,参数max_digits表示总位数,参数decimal_places表示小数位数 |
| FloatField | 浮点数 |
| DateField | 日期,参数auto_now每次保存时设置为当前时间,参数auto_now_add第一次被创建时设置为当前时间,默认都为False,不可组合 |
| TimeFoeld | 时间,参数同DateField |
| DateTimeField | 日期时间,参数同DateField |
| FileField | 上传文件字段 |
| ImageFiled | 继承于FileField,对上传的内容进行校验,确保是有效的图片 |
选项
null是数据库范畴的概念,blank是表单验证的范畴
|-----------------|------------------------------|
| 选项 | 说明 |
| null | 如果为True,表示允许为空,默认False |
| blank | 如果为True,表示允许为空白,默认False |
| db_column | 字段名称,若未指定,使用属性的名称 |
| db_index | 若值为True,则会为表中的字段创建索引,默认False |
| default | 指定默认值 |
| primary_key | 若为True,字段成为模型主键,默认False |
| unique | 如果为True,字段中的值不可重复,默认False |
外键
on_delete=
指外键被删除后被关联字段的数据要做什么操作
可选参数
-
CASCADE级联:删除主表数据时,连同外键表字段中的数据一起删除
-
PROTECT保护:通过抛出ProtecteError异常,无法删除主表中的数据
-
SET_NULL设置为NULL,仅在该字段null=True允许为空时,将关联字段数据置为空
-
SET_DEFAULT设置默认值:仅在该字段设置了默认值时可用
-
SET()设置为特定值或调用特定方法
-
DO_NOTHING:不做任何操作,如果数据库前置指明级联性,会抛出IntegrityError异常
返回一个对象=models.ForeignKey(外键类名,on_delete=[])
shell
作用
快速验证增删改查的结果,最终的代码还是要写在视图中
进入shell命令
python manage.py shell
增加数据
方式一,创建对象,一个对象就是一条数据
需要调用save()方法,保存
导入模型类
from bookmanager.book.models import BookInfo
book=BookInfo(
name="django",
pub_date="2000-1-1",
read_count="10"
)
book.save()
"""
mysql> select * from bookinfo
-> ;
+----+--------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+--------+---------------+-----------+------------+------------+
| 1 | django | 0 | 0 | 2000-01-01 | 10 |
+----+--------+---------------+-----------+------------+------------+
1 row in set (0.00 sec)
"""
方式二,使用objects
不需要save()
# objects相当于一个代理,直接跟数据库打交道
BookInfo.objects.create(
name="flask",
pub_date="2020-1-1",
read_count="100"
)
"""
mysql> select * from bookinfo ;
+----+--------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+--------+---------------+-----------+------------+------------+
| 1 | django | 0 | 0 | 2000-01-01 | 10 |
| 2 | flask | 0 | 0 | 2020-01-01 | 100 |
+----+--------+---------------+-----------+------------+------------+
2 rows in set (0.00 sec)
"""
更新数据
方式一get,需要调用save()方法
get查询,查询后返回一个对象,通过对象属性赋值来更改数据
from bookmanager.book.models import BookInfo
# get查询,查询后返回一个对象,通过对象属性赋值来更改数据
book=BookInfo.objects.get(id=1)
book.name="新版Django"
book.save()
"""
mysql> select * from bookinfo ;
+----+------------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+------------+---------------+-----------+------------+------------+
| 1 | 新版Django | 0 | 0 | 2000-01-01 | 10 |
| 2 | flask | 0 | 0 | 2020-01-01 | 100 |
+----+------------+---------------+-----------+------------+------------+
2 rows in set (0.00 sec)
"""
方式二filter,不需要调用save()方法
BookInfo.objects.filter(id=2).update(name="升级flask",pub_date="2024-2-2")
"""
>>> BookInfo.objects.filter(id=2).update(name="升级flask",pub_date="2024-2-2")
1
mysql> select * from bookinfo ;
+----+------------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+------------+---------------+-----------+------------+------------+
| 1 | 新版Django | 0 | 0 | 2000-01-01 | 10 |
| 2 | 升级flask | 0 | 0 | 2024-02-02 | 100 |
+----+------------+---------------+-----------+------------+------------+
2 rows in set (0.00 sec)
"""
删除数据
删除分为两种
物理删除:从硬盘上彻底删除
逻辑删除:修改标志位,给数据打上标签
方式一get
先使用get查询数据,然后调用对象的呃delete方法,不用调用save()方法
book=BookInfo.objects.get(id=1)
book.delete
"""
>>> book=BookInfo.objects.get(id=1)
>>> book.delete()
(1, {'book.PeopleInfo': 0, 'book.BookInfo': 1})
mysql> select * from bookinfo ;
+----+-----------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+-----------+---------------+-----------+------------+------------+
| 2 | 升级flask | 0 | 0 | 2024-02-02 | 100 |
+----+-----------+---------------+-----------+------------+------------+
1 row in set (0.00 sec)
"""
方式二filter
BookInfo.objects.filter(id=2).delete()
"""
>>> BookInfo.objects.filter(id=2).delete()
(1, {'book.PeopleInfo': 0, 'book.BookInfo': 1})
mysql> select * from bookinfo ;
Empty set (0.00 sec)
"""
运算符
|---------------------|--------------------------------|
| 运算符 | 说明 |
| exact等于 | id__exact=1,查询id=1 |
| contains包含 | name__contains="刘",查询名字中包含刘的 |
| endswith结尾 | name__endswith="刚",查询名字结尾包含刚的 |
| isnull=True为空 | name__isnull=True,查询名字为空的 |
| in=[]值是否在列表里面 | id__in=[1,3,5],查询id为1,3,5的数据 |
| gt大于 | id__gt=3,查询id大于3的数据 |
| gte大于等于 | id__gte=3,查询id大于等于3的数据 |
| lt小于 | id__lt=3,查询id小于3的数据 |
| lte小于等于 | id__lte=3,查询id小于等于3的数据 |
| year年份 | date__year=2024,查询日期年是2024年的数据 |
查询
基础查询
- get:只能查到一条数据,通常用于精确查询,如果不存在会抛出异常
- all:查询多个结果,返回的一个数组
- count:统计查询结果的数量
get查询
book=BookInfo.objects.get(id=3)
"""
>>> book=BookInfo.objects.get(id=3)
>>> book
<BookInfo: 内测flask>
mysql> select * from bookinfo ;
+----+-----------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+-----------+---------------+-----------+------------+------------+
| 3 | 内测flask | 0 | 0 | 2020-01-01 | 100 |
| 4 | django | 0 | 0 | 2000-01-01 | 10 |
+----+-----------+---------------+-----------+------------+------------+
2 rows in set (0.00 sec)
"""
all查询
books=BookInfo.object.all()
books
"""
>>> books=BookInfo.objects.all()
>>> books
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>]>
mysql> select * from bookinfo ;
+----+-----------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+-----------+---------------+-----------+------------+------------+
| 3 | 内测flask | 0 | 0 | 2020-01-01 | 100 |
| 4 | django | 0 | 0 | 2000-01-01 | 10 |
+----+-----------+---------------+-----------+------------+------------+
2 rows in set (0.00 sec)
"""
count统计查询
books_count=BookInfo.objects.all().count()
books_count
counts=BookInfo.objects.count()
counts
"""
>>> books_count=BookInfo.objects.all().count()
>>> books_count
2
>>> counts=BookInfo.objects.count()
>>> counts
2
mysql> select count(*) from bookinfo;
+----------+
| count(*) |
+----------+
| 2 |
+----------+
1 row in set (0.00 sec
"""
过滤查询
- filter过滤出多个结果,返回的是一个列表
- exclude排除掉符合条件剩下的结果,返回的也是一个列表
- get过滤第单一结果,只返回一个结果
filter查询
模型名.objects.filter(属性名__运算符=值)
BookInfo.objects.filter(id=4)
BookInfo.objects.filter(id__exact=4)
"""
>>> BookInfo.objects.filter(id=4)
<QuerySet [<BookInfo: django>]>
>>> BookInfo.objects.filter(id__exact=4)
<QuerySet [<BookInfo: django>]>
"""
exclude查询
模型名.objects.exclude(属性名__运算符=值)
BookInfo.objects.exclude(id=4)
BookInfo.objects.exclude(id__exact=4)
"""
>>> BookInfo.objects.exclude(id=4)
<QuerySet [<BookInfo: 内测flask>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
>>> BookInfo.objects.exclude(id__exact=4)
<QuerySet [<BookInfo: 内测flask>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
"""
get查询
模型名.objects.get(属性名__运算符=值)
BookInfo.objects.get(id=4)
BookInfo.objects.get(id__excat=4)
"""
>>> BookInfo.objects.get(id__exact=4)
<BookInfo: django>
>>> BookInfo.objects.get(id=4)
<BookInfo: django>
"""
F对象
对查询对象的属性进行比较,需要导入模块
from django.db.models import F
模型类名.objects.filter(属性名__运算符=F("第二个属性名"))
from django.db.models import F
BookInfo.objects.filter(read_count__gt=F("comment_count"))
"""
>>> from django.db.models import F
>>> BookInfo.objects.filter(read_count__gt=F("comment_count"))
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>]>
mysql> select * from bookinfo ;
+----+-----------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+-----------+---------------+-----------+------------+------------+
| 3 | 内测flask | 0 | 0 | 2020-01-01 | 100 |
| 4 | django | 0 | 0 | 2000-01-01 | 10 |
| 5 | python | 10 | 0 | 2024-01-01 | 0 |
| 6 | java | 200 | 0 | 2022-01-01 | 0 |
| 7 | html | 50 | 0 | 2020-01-01 | 0 |
+----+-----------+---------------+-----------+------------+------------+
5 rows in set (0.00 sec)
"""
Q对象
可用实现逻辑与和逻辑或的查询
需要导入模块
from django.db.models import Q
并且查询
BookInfo.objects.filter(id=5).filter(read_count__lt=10)
BookInfo.objects.filter(id=5,read_count__lt=10)
"""
>>> BookInfo.objects.filter(id=5).filter(read_count__lt=10)
<QuerySet [<BookInfo: python>]>
>>> BookInfo.objects.filter(id=5,read_count__lt=10)
<QuerySet [<BookInfo: python>]>
mysql> select * from bookinfo ;
+----+-----------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+-----------+---------------+-----------+------------+------------+
| 3 | 内测flask | 0 | 0 | 2020-01-01 | 100 |
| 4 | django | 0 | 0 | 2000-01-01 | 10 |
| 5 | python | 10 | 0 | 2024-01-01 | 0 |
| 6 | java | 200 | 0 | 2022-01-01 | 0 |
| 7 | html | 50 | 0 | 2020-01-01 | 0 |
+----+-----------+---------------+-----------+------------+------------+
5 rows in set (0.00 sec)
""
Q查询
或查询:模型类名.objects.filter(Q(属性名__运算符=值)|Q(属性名__运算符=值)|....)
from django.db.models import Q
BookInfo.objects.filter(Q(id=5)|Q(read_count__lt=10))
"""
>>> BookInfo.objects.filter(Q(id=5)|Q(read_count__lt=10))
<QuerySet [<BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
"""
并且查询:模型类名.objects.filter(Q(属性名__运算符=值)&Q(属性名__运算符=值)&.....)
BookInfo.objects.filter(Q(id=5)&Q(read_count__lt=10))
"""
>>> BookInfo.objects.filter(Q(id=5)&Q(read_count__lt=10))
<QuerySet [<BookInfo: python>]>
"""
非not查询:模型类名.objects.filter(~Q(属性名__运算符=值))
BookInfo.objects.filter(~Q(id=5)&Q(read_count__lt=10))
BookInfo.objects.filter(~Q(id=5)&~Q(read_count__lt=10))
BookInfo.objects.filter(~Q(id=5)|Q(read_count__lt=10))
BookInfo.objects.filter(~Q(id=5)|~Q(read_count__lt=10))
"""
>>> BookInfo.objects.filter(~Q(id=5)&Q(read_count__lt=10))
<QuerySet [<BookInfo: java>, <BookInfo: html>]>
>>> BookInfo.objects.filter(~Q(id=5)&~Q(read_count__lt=10))
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>]>
>>> BookInfo.objects.filter(~Q(id=5)|Q(read_count__lt=10))
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
>>> BookInfo.objects.filter(~Q(id=5)|~Q(read_count__lt=10))
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>, <BookInfo: java>, <BookInfo: html>]>
"""
聚合函数
Sum、Max、Min、Avg、Count
模块名.objects.aggregate(聚合函数("字段名"))
需要导入模块
from django.db.models import Sum,Max,Min,Avg,Count
from django.db.models import Sum,Max,Min,Count,Avg
BookInfo.objects.aggregate(Sum("read_count"))
BookInfo.objects.aggregate(Avg("read_count"))
BookInfo.objects.aggregate(Max("read_count"))
BookInfo.objects.aggregate(Min("read_count"))
BookInfo.objects.aggregate(Count("read_count"))
"""
>>> from django.db.models import Sum,Max,Min,Count,Avg
>>> BookInfo.objects.aggregate(Sum("read_count"))
{'read_count__sum': 110}
>>> BookInfo.objects.aggregate(Avg("read_count"))
{'read_count__avg': 22.0}
>>> BookInfo.objects.aggregate(Max("read_count"))
{'read_count__max': 100}
>>> BookInfo.objects.aggregate(Min("read_count"))
{'read_count__min': 0}
>>> BookInfo.objects.aggregate(Count("read_count"))
{'read_count__count': 5}
"""
排序
升序
BookInfo.object.all().order_by("read_count")
"""
>>> BookInfo.objects.all().order_by("read_count")
<QuerySet [<BookInfo: python>, <BookInfo: java>, <BookInfo: html>, <BookInfo: django>, <BookInfo: 内测flask>]>
"""
降序
BookInfo.objects.all().order_by("-read_count")
"""
>>> BookInfo.objects.all().order_by("-read_count")
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
"""
关联查询
关联查询往往是查询通过外键关联两个表的数据
系统会自动在主表中添加小写外键类名_set的方法
一对多模型类对象.多对应的模型类名小写_set
# 需要拿到主表数据的一个对象
# 然后去调用关联表的模型类_set
book=BookInfo.objects.get(id=6)
book.peopleinfo_set.all()
"""
>>> book=BookInfo.objects.get(id=6)
>>> book.peopleinfo_set.all()
<QuerySet [<PeopleInfo: 詹姆斯·高斯林>, <PeopleInfo: 余麻子>]>
mysql> select * from peopleinfo ;
+----+----------------+--------+---------+-------------+-----------+
| id | name | gender | book_id | description | is_delete |
+----+----------------+--------+---------+-------------+-----------+
| 1 | 吉多·范罗苏姆 | 1 | 3 | python之夫 | 0 |
| 4 | 吉多·范罗苏姆 | 1 | 5 | python之夫 | 0 |
| 5 | 詹姆斯·高斯林 | 1 | 6 | java之夫 | 0 |
| 6 | 余麻子 | 1 | 6 | java继夫 | 0 |
+----+----------------+--------+---------+-------------+-----------+
4 rows in set (0.00 sec)
mysql> select * from bookinfo ;
+----+-----------+---------------+-----------+------------+------------+
| id | name | comment_count | is_delete | pub_date | read_count |
+----+-----------+---------------+-----------+------------+------------+
| 3 | 内测flask | 0 | 0 | 2020-01-01 | 100 |
| 4 | django | 0 | 0 | 2000-01-01 | 10 |
| 5 | python | 10 | 0 | 2024-01-01 | 0 |
| 6 | java | 200 | 0 | 2022-01-01 | 0 |
| 7 | html | 50 | 0 | 2020-01-01 | 0 |
+----+-----------+---------------+-----------+------------+------------+
5 rows in set (0.00 sec)
"""
多对一的模型类对象.多对应的模型类中的关系类属性名
因为从表的外键已经指向了一个主表对象, 所以可以直接获取从表对象 来调用主表模型类,可以获得主表模型类的对象 ,也可以获取主表模型类对象的属性
people=PeopleInfo.objects.get(id=1)
people.book.all()
"""
>>> people=PeopleInfo.objects.get(id=1)
# 获取主表模型类对象
>>> people.book
<BookInfo: 内测flask>
# 获取主表模型类对象的属性
>>> people.book.name
'内测flask'
"""
关联过滤查询
语法格式:模型类名.objects.(关联模型类名小写__字段名__运算符=值)
从一的数据表中查询符合条件的从表的值(左一右多)
BookInfo.objects.filter(peopleinfo__name__exact="余麻子")
BookInfo.objects.filter(peopleinfo__name__contains="余")
"""
>>> BookInfo.objects.filter(peopleinfo__name__exact="余麻子")
<QuerySet [<BookInfo: java>]>
>>> BookInfo.objects.filter(peopleinfo__name__contains="余")
<QuerySet [<BookInfo: java>]>
"""
根据从表的数据查询主表数据(使用外键)
PeopleInfo.objects.filter(book.name__exact="python")
""""
>>> PeopleInfo.objects.filter(book__name__exact="python")
<QuerySet [<PeopleInfo: 吉多·范罗苏姆>]>
"""
查询结果集QuerySet
什么是结果集,必须是结果集才有两大特性
返回的查询结果不是单一的数据,而是一个集合QuerySet
两大特性(影响效率,在views视图中不执行就不不会消耗资源)
-
惰性执行:只有用的时候才会去执行,例如
在数据库中之句话并没有执行
book=BookInfo.objects.all()
当需要用到book时,才会请求数据库返回数据
book
"""
book=BookInfo.objects.all()
book # 这是才会去看book是什么数据
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>"""
-
缓存:使用同一个查询集(QuerySet),第一次使用会直接查询 ,然后把结果缓存下来,再次使用结果集 时候就会用到这个缓存数据,减少数据库查询的次数
这句话返回的是一个结果集QuerySet,它可以被缓存到内存中
books=BookInfo.objects.all()
"""
books=BookInfo.objects.all()
books
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
[book.id for book in books]
[3, 4, 5, 6, 7]
"""
限制查询集(切片操作)
不支持复数索引
# 返回了一个结果集合,可以操作下标索引
books=BookInfo.objects.all()
"""
>>> books=BookInfo.objects.all()
>>> books
<QuerySet [<BookInfo: 内测flask>, <BookInfo: django>, <BookInfo: python>, <BookInfo: java>, <BookInfo: html>]>
>>> books[1]
<BookInfo: django>
>>> books[0:1]
<QuerySet [<BookInfo: 内测flask>]>
""""