from teatcher.models import Student 导入app(teatcher)下的模型(Student) In [11]: res = Student.objects.all().queryIn [12]: print(res)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`sex`, `teatcher_student`.`age`, `teatcher_student`.`qq`, `teatcher_student`.`phone`, `teatcher_student`.`c_time`, `teatcher_student`.`m_time` FROM `teatcher_student`# Student.ojbects.all() 和select * from Student 效果一样. 返回是object
1.常用的模型字段类型
https://docs.djangoproject.com/en/2.1/ref/models/fields/#field-types
2.字段的常用参数
官方文档：https://docs.djangoproject.com/en/2.1/ref/models/fields/#field-options
id = models.IntegerField(primary_key=True) # 主键
mame = models.CharField(max_length=50,unique=True) # unqiue 唯一
num = models.CharField('班级编号203班,102班',max_length=20, unique=True) 备注,最大长度,唯一
qq = models.CharField(max_length=20, default='') # 字符类型
phone = models.CharField(max_length=30,default='')
c_time = models.DateTimeField('创建时间', auto_now_add=True) # auto_now_add 只加一次
m_time = models.DateTimeField('修改时间', auto_now=True) # auto_now 每次修改 会更新
3.常用查询*****
通过模型类上的管理器来构造QuerySet。
– 模型类上的管理器是啥？
**模型类.objects:
如: Student.objects object 是 Student 实例的管理器
– QuerySet 表示数据库中对象的集合。
等同于select 语句。 惰性的
案例：
– first() 获取第一条 返回的是对象
– last() 获取最后一条 返回的也是一个对象
In [12]: Student.objects.first()
Out[12]: <Student: 啊呆-18> #返回对象In [13]: Student.objects.last()
Out[13]: <Student: 小红-21>
In [20]: res = Student.objects.last()
In [21]: print(res)
小红-21
In [22]: res .qq
Out[22]: ‘28456’
In [23]: print(res)
小红-21
思考：排序规则？ 默认通过主键。通过_meta 设置
– get(**kwargs) 根据给定的条件，获取一个对象，如果有多个对象符合，保存
Student.objects.get(id=1) #get 和 主键配合,, get(pk=1) ,获取到多条结果时,会报错.
Out[29]: <Student: 啊呆-18>
– all() 获取所有记录 返回的是queryset
– filter(**kwargs) 根据给定的条件，获取一个过滤后的queryset，多个条件使用and连接。
In [32]: Student.objects.filter(age=18)
Out[32]: <QuerySet [<Student: 啊呆-18>, <Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>]>In [33]: Student.objects.filter(age=18,sex=1) 多个条件','分割
Out[33]: <QuerySet [<Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>]>
In [35]: res = Student.objects.filter(age=18,sex=1) #返回 对象集
In [36]: res[0].name
Out[36]: ‘小张’
– exclude(**kwargs) 跟filter使用方法一致，作用想反，它是排除。
# exclude 不包含的意思.不包含 age=18,sex=1的
In [38]: res = Student.objects.exclude(age=18,sex=1) In [39]: print(res)
<QuerySet [<Student: 啊呆-18>, <Student: 小绿-19>, <Student: 小红-21>]>In [45]:print(res.query)
In [45]:SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`sex`, `teatcher_student`.`age`, `teatcher_student`.`qq`, `teatcher_student`.`phone`, `teatcher_student`.`c_time`, `teatcher_student`.`m_time` FROM `teatcher_student` WHERE NOT (`teatcher_student`.`age` = 18 AND `teatcher_student`.`sex` = 1)
– 多条件的OR连接 用到Q对象，django.db.models.Q
In [41]: from django.db.models import Q Student.objects.filter(Q(age=0)|Q(age=18))'
<QuerySet [<Student: 啊呆-18>, <Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>]>
QuerySet[0].name 取值 ,<><表示是一个对象>
– values(*fields) 返回一个queryset，返回一个字典列表，而不是数据对象。
In [50]: Student.objects.values('name')
Out[50]: <QuerySet [{'name': '啊呆'}, {'name': '小张'}, {'name': '小黄'}, {'name': '小兰'}, {'name': '小绿'}, {'name': '小红'}]>
In [54]: print(res.query)
SELECT `teatcher_student`.`name` FROM `teatcher_student`
In [51]: Student.objects.values('name','sex')
Out[51]: <QuerySet [{'name': '啊呆', 'sex': 0}, {'name': '小张', 'sex': 1}, {'name': '小黄', 'sex': 1}, {'name': '小兰', 'sex': 1}, {'name': '小绿', 'sex': 0}, {'name':x': 0}]>
– only(*fiels) 返回querySet ，对象列表，注意only一定包含主键字段
In [55]: res =Student.objects.only('name') In [58]: print(res.query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name` FROM `teatcher_student`In [59]: print(res)
<QuerySet [<Student: 啊呆-18>, <Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>, <Student: 小绿-19>, <Student: 小红-21>]>
– defer(*fields) 返回一个QuerySet，作用和only相反
不包含 *fidelfs 的记录
In [60]: res =Student.objects.defer('name') In [61]: print(res.query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`sex`, `teatcher_student`.`age`, `teatcher_student`.`qq`, `teatcher_student`.`phone`, `teatcher_student`.`c_time`, `teatcher_student`.`m_time` FROM `teatcher_student`In [62]: print(res)
<QuerySet [<Student: 啊呆-18>, <Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>, <Student: 小绿-19>, <Student: 小红-21>]>
– order_by(*fields) 根据给定的字段来排序 默认是顺序，字段名前加上 ‘-’代表反序
– 切片 和python的列表切片用法相似，不支持负索引，数据量大时不用步长
*** 切片过后，不再支持，附加过滤条件与排序
In [63]: res =Student.objects.defer('name').order_by('name') In [64]: print(res)
<QuerySet [<Student: 啊呆-18>, <Student: 小兰-18>, <Student: 小张-18>, <Student: 小红-21>, <Student: 小绿-19>, <Student: 小黄-18>]>In [65]: print(res.query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`sex`, `teatcher_student`.`age`, `teatcher_student`.`qq`, `teatcher_student`.`phone`, `teatcher_student`.`c_time`, `teatcher_student`.`m_time` FROM `teatcher_student` ORDER BY `teatcher_student`.`name` ASC
查询结果 切片
In [9]: Student.objects.all()
Out[9]: <QuerySet [<Student: 啊呆-18>, <Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>, <Student: 小绿-19>, <Student: 小红-21>]>In [10]: Student.objects.all()[2:4] # 查询返回结果中的第三到第四条
Out[10]: <QuerySet [<Student: 小黄-18>, <Student: 小兰-18>]>
print(Student.objects.all()[2:4].query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`sex`, `teatcher_student`.`age`, `teatcher_student`.`qq`, `teatcher_student`.`phone`, `teatcher_student`.`c_time`, `teatcher_student`.`m_time` FROM `teatcher_student` LIMIT 2 OFFSET 2
– 常用查询条件 filter，exclude， get
– exact
(字段名__exact=19) 等同 (字段=19)
Student.objects.get(age__exact=19)
Out[15]: <Student: 小绿-19>
– iexact
In [21]: Student.objects.create(name='zhuoDa') # 字段=xXXXx i 表示 忽略大小写
Out[21]: <Student: zhuoDa-0>In [22]: Student.objects.only('name').filter(name__iexact='zhuoda')
Out[22]: <QuerySet [<Student: zhuoda-0>, <Student: Zhuoda-0>, <Student: ZhuoDa-0>, <Student: zhuoDa-0>]>
– contains
– icontains
- contains # 包含 like %xxx%
- icontains# 忽略大小写的 包含 like %xxx%
BINARY 关键字,区分大小写
In [25]: print(Student.objects.only('name').filter(name__contains='da').query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name` FROM `teatcher_student` WHERE `teatcher_student`.`name` LIKE BINARY %da%In [26]: print(Student.objects.only('name').filter(name__icontains='da').query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name` FROM `teatcher_student` WHERE `teatcher_student`.`name` LIKE %da%
– in
In [34]: Student.objects.only('name').filter(name__in=['小张','小黄']) # (name__in=[1,2,3,4,5])
Out[34]: <QuerySet [<Student: 小张-18>, <Student: 小黄-18>]>
– range
In [36]: Student.objects.only('name').filter(age__range=(5,50)) # range(小,大) 只能 从小 到大 写.
Out[36]: <QuerySet [<Student: 啊呆-18>, <Student: 小张-18>, <Student: 小黄-18>, <Student: 小兰-18>, <Student: 小绿-19>, <Student: 小红-21>]>
In [37]: print(Student.objects.only(‘name’,’age’).filter(age__range=(5,50)).query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`age` FROM `teatcher_student` WHERE `teatcher_student`.`age` BETWEEN 5 AND 50
– gt
– gte
– lt
– lte
In [38]: print(Student.objects.only('name','age').filter(age__gt=5).query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`age` FROM `teatcher_student` WHERE `teatcher_student`.`age` > 5
– startswith # 什么开头的
– istartswith # 什么 开头 忽略大小写
– endswith # 什么结尾的
– iendswith # 什么 结尾 忽略大小写
In [39]: print(Student.objects.only('name','age').filter(name__startswith='z').query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`age` FROM `teatcher_student` WHERE `teatcher_student`.`name` LIKE BINARY z%In [40]: print(Student.objects.only('name','age').filter(name__istartswith='z').query)
SELECT `teatcher_student`.`id`, `teatcher_student`.`name`, `teatcher_student`.`age` FROM `teatcher_student` WHERE `teatcher_student`.`name` LIKE z%
– isnull True False 对应 IS NULL IS NOT NULL
– 聚合
from django.db.models import Count, Avg, Max, Min, Sum
通过queryset的aggregate方法
Student.objects.aggregate(age_avg=Avg(‘age’)) # 计算平均年龄
– count
– 平均值 Avg
– 分组，聚合
结合 Values,annotate 和聚合方法一起实现
In [42]: from django.db.models import Count,Avg,Max,Min,Sum
In [44]: Student.objects.aggregate(age_avg=Avg('age')) #(临时字段名= Avg('字段'))
Out[44]: {'age_avg': 11.2}In [46]: Student.objects.aggregate(ages=Min('age'))
Out[46]: {'ages': 0}In [47]: Student.objects.aggregate(ages=Max('age'))
Out[47]: {'ages': 21}In [48]: Student.objects.aggregate(ages=Count('age'))
Out[48]: {'ages': 10}
查询男生有几个，女生有几个
In [49]: Student.objects.values('sex').annotate(num=Count('sex'))
Out[49]: <QuerySet [{'sex': 0, 'num': 7}, {'sex': 1, 'num': 3}]>In [50]: print(Student.objects.values('sex').annotate(num=Count('sex')).query)
SELECT `teatcher_student`.`sex`, COUNT(`teatcher_student`.`sex`) AS `num` FROM `teatcher_student` GROUP BY `teatcher_student`.`sex` ORDER BY NULL
****按字段的小写 排序
关键字:Lower
In [6]: from django.db.models.functions import Lower In [7]: student.objects.all()
Out[7]:^[[A^[[A<QuerySet [<student: 第一条-18>, <student: 第二条-18>, <student: 第三条-22>, <student: 第四条-18>]>In [8]: student.objects.order_by(Lower('name'))
Out[8]: <QuerySet [<student: 第一条-18>, <student: 第三条-22>, <student: 第二条-18>, <student: 第四条-18>]>In [9]: print(student.objects.order_by(Lower('name')).query)
SELECT `student_student`.`id`, `student_student`.`name`, `student_student`.`sex`, `student_student`.`age`, `student_student`.`qq`, `student_student`.`phone`, `student_student`.`c_time` FROM `student_student` ORDER BY LOWER(`student_student`.`name`) ASC
非数值类型的倒序
In [12]: student.objects.order_by(Lower('name').desc())
Out[12]: <QuerySet [<student: 第四条-18>, <student: 第二条-18>, <student: 第三条-22>, <student: 第一条-18>]>
In [13]: print(student.objects.order_by(Lower(‘name’).desc()).query)
SELECT `student_student`.`id`, `student_student`.`name`, `student_student`.`sex`, `student_student`.`age`, `student_student`.`qq`, `student_student`.`phone`, `student_student`.`c_time` FROM `student_student` ORDER BY LOWER(`student_student`.`name`) DESC
4.表关系实现
