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)
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())
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)
- 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)
- 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)
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
增
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()
删
In [15]: s.grade =None In [16]: s.save() In [17]: s= Student.objects.first() In [18]: s.grade
改
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>
查
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'
- 反向
增
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>]>
删
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 []>
改
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>]>
查
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
-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>
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
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%
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%)
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
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%