django第七课模型第三讲 – 风扇1121

1.自定义主键字段的创建
  AutoFiled(pirmary_key=True) # 一般不会自定义

  

class Grade(models.Model):
    idd = models.AutoField(primary_key=True)
    name = models.CharField(max_length=20)
    num = models.CharField(max_length=20)

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 2.order_by  asc desc

  小写排序默认是asc,倒叙的时候需要调用到desc

In [4]: from django.db.models.functions import Lower                                                       

In [5]: res = Student.objects.order_by(Lower('name'))                                                      

In [6]: print(res.query)                                                                                   
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`c_time` FROM `teacher_student` ORDER BY LOWER(`teacher_student`.`name`) ASC

In [7]: res = Student.objects.order_by(Lower('name').desc()) 

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1. 表关系的创建
– OneToOne
student = models.OneToOneField(‘Student’, on_delete=models.CASCADE)

  学生和学生详情表通过外键关联

  

class Studentdetail(models.Model):
    num = models.CharField(max_length=20,default=' ')
    collage = models.CharField(max_length=20,default=' ')
    student = models.OneToOneField('Student',on_delete=models.CASCADE)





mysql> show tables;
+-----------------------+
| Tables_in_crm         |
+-----------------------+
| django_migrations     |
| teacher_grade         |
| teacher_student       |
| teacher_studentdetail |
+-----------------------+
4 rows in set (0.00 sec)

mysql> desc teacher_studentdetail;
+------------+-------------+------+-----+---------+----------------+
| Field      | Type        | Null | Key | Default | Extra          |
+------------+-------------+------+-----+---------+----------------+
| id         | int(11)     | NO   | PRI | NULL    | auto_increment |
| num        | varchar(20) | NO   |     | NULL    |                |
| collage    | varchar(20) | NO   |     | NULL    |                |
| student_id | int(11)     | NO   | UNI | NULL    |                |
+------------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

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– OneToMany
grade = models.ForeignKey(‘Grade’, on_delete=models.SET_NULL, null=True)

学生和班级是一对多的关系

 1 class Student(models.Model):
 2     name = models.CharField(max_length=20)
 3     age = models.SmallIntegerField(default=0)
 4     sex =models.SmallIntegerField(default=1)
 5     qq = models.CharField(max_length=20,default='')
 6     phone = models.CharField(max_length=20)
 7     
 8     c_time = models.DateTimeField(verbose_name='创建时间',auto_now_add=True)
 9     e_time = models.DateTimeField(verbose_name='修改时间', auto_now=True)
10 grade = models.ForeignKey('Grade',on_delete=models.SET_NULL,null=True)
11 
12 
13 
14 
15 class Grade(models.Model):
16     idd = models.AutoField(primary_key=True)
17     name = models.CharField(max_length=20)
18     num = models.CharField(max_length=20)

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– ManyToMany

多对多需要通过第三张表来实现

课程表和学生表是多对多关系

 1 class Course(models.Model):
 2     name = models.CharField('课程名称',max_length=20)
 3     student = models.ManyToManyField('Student')
 4 
 5 
 6 mysql> desc teacher_course;
 7 +-------+-------------+------+-----+---------+----------------+
 8 | Field | Type        | Null | Key | Default | Extra          |
 9 +-------+-------------+------+-----+---------+----------------+
10 | id    | int(11)     | NO   | PRI | NULL    | auto_increment |
11 | name  | varchar(20) | NO   |     | NULL    |                |
12 +-------+-------------+------+-----+---------+----------------+
13 2 rows in set (0.00 sec)

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第三张表:

class Enroll(models.Model):
    student = models.ForeignKey('Student',on_delete=models.CASCADE)
    course = models.ForeignKey('Course',on_delete=models.CASCADE)
    pay = models.FloatField('缴费金额',default=0)
    c_time = models.DateTimeField('报名时间',auto_now_add=True)
mysql> desc  teacher_enroll;
+------------+-------------+------+-----+---------+----------------+
| Field      | Type        | Null | Key | Default | Extra          |
+------------+-------------+------+-----+---------+----------------+
| id         | int(11)     | NO   | PRI | NULL    | auto_increment |
| pay        | double      | NO   |     | NULL    |                |
| c_time     | datetime(6) | NO   |     | NULL    |                |
| course_id  | int(11)     | NO   | MUL | NULL    |                |
| student_id | int(11)     | NO   | MUL | NULL    |                |
+------------+-------------+------+-----+---------+--------------

2. 关联表的数据操作
– OneToMany
– 正向 一个模型如果定义了一个外键字段,通过这个模型操作外键

In [3]: s = Student()                                                                                      


In [5]: Student.objects.all()                                                                              
Out[5]: <QuerySet []>

In [6]: s.name='xinlan'                                                                                    

In [7]: Student.objects.all()                                                                              
Out[7]: <QuerySet []>

In [9]: g1 = Grade.objects.first()                                                               

In [10]: g1                                                                                                
Out[10]: <Grade: 33qi-djangokuangjia>

In [11]: s.grade=g1                                                                                        

In [12]: s.save() 










In [13]: s2 = Student(name='weimingka')                                                                    

In [14]: g2 = Grade.objects.last()                                                                         

In [15]: s2.grade_id=g2.idd 
In [16]: s2.save()

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In [15]: s.grade =None                                                                                     

In [16]: s.save()                                                                                          

In [17]: s= Student.objects.first()                                                                        

In [18]: s.grade

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In [8]: g2=Grade.objects.last()                                                                            

In [9]: g2                                                                                                 
Out[9]: <Grade: 34qi-pachou>

In [10]: s.grade= g2                                                                                       

In [11]: s.save()             
In [14]: s.grade                                                                                           
Out[14]: <Grade: 34qi-pachou>

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In [37]: s2                                                                                                
Out[37]: <Student: weimingkai-0>

In [38]: s2.name                                                                                           
Out[38]: 'weimingkai'

In [39]: s2.grade.name                                                                                     
Out[39]: 'pachou'

In [40]: s2.grade.num                                                                                      
Out[40]: '34qi'

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– 反向

In [41]: g3 =Grade.objects.create(name='jinjie',num='40qi')                                                

In [42]: g3.student_set.create(name='lipenghao')                                                           
Out[42]: <Student: lipenghao-0>

In [43]: g3.student_set.add(s)                                                                             

In [44]: g3.student_set.all()                                                                              
Out[44]: <QuerySet [<Student: xinlan-0>, <Student: lipenghao-0>]>

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删除
In [49]: g3.student_set.remove(s)                                                                          

In [50]: g3.student_set.all()                                                                              
Out[50]: <QuerySet [<Student: lipenghao-0>]>


清空
In [51]: g3.student_set.clear()                                                                            

In [52]: g3.student_set.all()                                                                              
Out[52]: <QuerySet []>

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先执行clear清空,在添加列表

In [54]: g3.student_set.set([s,s2])                                                                        

In [55]: g3.student_set.all()                                                                              
Out[55]: <QuerySet [<Student: xinlan-0>, <Student: weimingkai-0>]>

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出现学生表里面的课程

In [59]: res = Student.objects.filter(grade__name='djangokuangjia')                                        

In [60]: print(res.query)                                                                                  
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_time` FROM `teacher_student` INNER JOIN `teacher_grade` ON (`teacher_student`.`grade_id` = `teacher_grade`.`idd`) WHERE `teacher_grade`.`name` = djangokuangjia

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-Many-to-Many
*** 指定了中间表,add,remove,set 都不能用,必须用中间表

In [73]: Enroll.objects.create(student=s2,course=c3)                                                       
Out[73]: <Enroll: weimingkai-0-english>
In [75]: c1.student                                                                                        
Out[75]: <django.db.models.fields.related_descriptors.create_forward_many_to_many_manager.<locals>.ManyRelatedManager at 0x7fa557bec5f8>

-One-to-One

In [80]: sd = Studentdetail.objects.create(num=2019020001,collage='jialidun',student=s2)                   

In [81]: sd                                                                                                
Out[81]: <Studentdetail: Studentdetail object (1)>

In [82]: sd.student                                                                                        
Out[82]: <Student: weimingkai-0>

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反向

 

 3. 跨表查询

  查询男生报了什么课程?

  

In [88]: res = Course.objects.filter(student__sex=1)                                                       

In [89]: print(res.query)                                                                                  
SELECT `teacher_course`.`id`, `teacher_course`.`name` FROM `teacher_course` INNER JOIN `teacher_enroll` ON (`teacher_course`.`id` = `teacher_enroll`.`course_id`) INNER JOIN `teacher_student` ON (`teacher_enroll`.`student_id` = `teacher_student`.`id`) WHERE `teacher_student`.`sex` = 1

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查询所有报名Python课程的学员

In [90]: res = Student.objects.filter(course__name__contains='python')                                     

In [91]: print(res.query)                                                                                  
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_time` FROM `teacher_student` INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) INNER JOIN `teacher_course` ON (`teacher_enroll`.`course_id` = `teacher_course`.`id`) WHERE `teacher_course`.`name` LIKE BINARY %python%

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查询所欲报名英语33期的学园

In [93]: print(res.query)                                                                                  
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_time` FROM `teacher_student` INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) INNER JOIN `teacher_course` ON (`teacher_enroll`.`course_id` = `teacher_course`.`id`) INNER JOIN `teacher_grade` ON (`teacher_student`.`grade_id` = `teacher_grade`.`idd`) WHERE (`teacher_course`.`name` LIKE BINARY %english% AND `teacher_grade`.`num` LIKE BINARY %33%)

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缴费小于3000的学员

                                                                                                           
In [95]: res = Student.objects.filter(enroll__pay__lt=3000)                                                

In [96]: print(res.query)                                                                                  
SELECT `teacher_student`.`id`, `teacher_student`.`name`, `teacher_student`.`age`, `teacher_student`.`sex`, `teacher_student`.`qq`, `teacher_student`.`phone`, `teacher_student`.`grade_id`, `teacher_student`.`c_time`, `teacher_student`.`e_time` FROM `teacher_student` INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) WHERE `teacher_enroll`.`pay` < 3000.0

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报名python的课有哪些

In [99]: res=Grade.objects.filter(student__course__name__contains='python')                                

In [100]: print(res.query)                                                                                 
SELECT `teacher_grade`.`idd`, `teacher_grade`.`name`, `teacher_grade`.`num` FROM `teacher_grade` INNER JOIN `teacher_student` ON (`teacher_grade`.`idd` = `teacher_student`.`grade_id`) INNER JOIN `teacher_enroll` ON (`teacher_student`.`id` = `teacher_enroll`.`student_id`) INNER JOIN `teacher_course` ON (`teacher_enroll`.`course_id` = `teacher_course`.`id`) WHERE `teacher_course`.`name` LIKE BINARY %python%

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