only与defer
only括号内放字段 查询结果是一个列表套一个个的数据对象
这些数据对象点括号内的字段属性不会再查询数据库 直接就是对象获取属性
也支持点击括号内没有的字段 但是每点击一次就会重新走一次数据库查询 效率极低
defer与only是互为反操作
defer括号内放什么字段 查询出来的对象就没有该字段属性
如果你要点击 每点击一次就要重新走一次数据
而你如果点击了非括号内的字段 就不会走数据库 仅仅是对象属性的操作
select_related与prefetch_related
select_related与prefetch_related
select_related括号内只能放外键字段 并且外键字段的类型只能是一对多 或者 一对一 不能是多对多
内部是自动连表操作 会将括号内外键字段所关联的表 与当前表自动拼接成一张表
然后将表中的数据一个个查询出来封装成一个个的对象
这样做的好处就在于跨表也不需要重复的走数据库了 减轻数据库的压力
select_related括号内可以放多个外键字段 都号隔开 会将多个外键字段关联的表与当前表全部拼成一张大表
耗时:数据库层面需要先连表
prefetch_related内部是子查询
会自动帮你按步骤查询多张表 然后将查询的结果封装到对象中
给用户的感觉好像还是连表操作
括号内支持传多个外键字段 并且没有类型限制
特点:每放一个外键字段 就会多走一条sql语句 多查询一张表
耗时:查询的次数长
两者之间的优缺点
结合实际情况 表的大小
两张表都特别大的情况下 连表操作 可能耗时更多
MTV与MVC模型
MTV:
M:models 模型层
T:templates 模板层
V:views 视图层
MVC:
M:models 模型层
V:views 视图层
C:controllar路由匹配
choices参数
如果存储的数字不在关系中又会怎么样
能够正常存储
也能够正常获取(数字)
只要是choices字段类型 在获取值的时候 统一句式
get_字段名_display()
from django.db import models # # # Create your models here. class User(models.Model): username = models.CharField(max_length=64) password = models.IntegerField() gender_choices = ( (1,'男'), (2,'女'), (3,'其他'), ) gender = models.IntegerField(choices=gender_choices) # 该字段存数字 """ 1.如果存储的数字在我们提前定义好的关系中会怎么样 2.如果存储的数字不在关系中又会怎么样 能够正常存储 也能够正常获取(数字) """
# Create your tests here. import os if __name__ == "__main__": os.environ.setdefault("DJANGO_SETTINGS_MODULE", "day55.settings") import django django.setup() from app01 import models user_obj = models.User.objects.get(pk=1) user_obj1 = models.User.objects.get(pk=4) # print(user_obj.gender) # print(user_obj1.gender) # print(user_obj.get_gender_display()) print(user_obj1.get_gender_display()) # 没有对应关系 获取到的还是数字本身 """ 只要是choices字段类型 在获取值的时候 统一句式 get_字段名_display() """
实际例子:
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from django.db import models # Create your models here. # rbac权限相关表格 class User(models.Model): name = models.CharField(max_length=32) pwd = models.CharField(max_length=32) roles = models.ManyToManyField(to='Role') def __str__(self): return self.name class Role(models.Model): title = models.CharField(max_length=32) permissions = models.ManyToManyField(to='Permission') def __str__(self): return self.title class Permission(models.Model): title = models.CharField(max_length=32) url = models.CharField(max_length=32) code = models.CharField(max_length=32,default='list') def __str__(self): return self.title # CRM相关内部表 class School(models.Model): """ 校区表 如: 北京沙河校区 上海校区 """ title = models.CharField(verbose_name='校区名称', max_length=32) def __str__(self): return self.title class Course(models.Model): """ 课程表 如: Linux基础 Linux架构师 Python自动化开发精英班 Python自动化开发架构师班 Python基础班 go基础班 """ name = models.CharField(verbose_name='课程名称', max_length=32) def __str__(self): return self.name class Department(models.Model): """ 部门表 市场部 1000 销售 1001 """ title = models.CharField(verbose_name='部门名称', max_length=16) code = models.IntegerField(verbose_name='部门编号', unique=True, null=False) def __str__(self): return self.title class UserInfo(models.Model): """ 员工表 """ name = models.CharField(verbose_name='员工姓名', max_length=16) email = models.EmailField(verbose_name='邮箱', max_length=64) depart = models.ForeignKey(verbose_name='部门', to="Department",to_field="code") user=models.OneToOneField("User",default=1) def __str__(self): return self.name class ClassList(models.Model): """ 班级表 如: Python全栈 面授班 5期 10000 2017-11-11 2018-5-11 """ school = models.ForeignKey(verbose_name='校区', to='School') course = models.ForeignKey(verbose_name='课程名称', to='Course') semester = models.IntegerField(verbose_name="班级(期)") price = models.IntegerField(verbose_name="学费") start_date = models.DateField(verbose_name="开班日期") graduate_date = models.DateField(verbose_name="结业日期", null=True, blank=True) memo = models.CharField(verbose_name='说明', max_length=256, blank=True, null=True, ) teachers = models.ManyToManyField(verbose_name='任课老师', to='UserInfo',limit_choices_to={'depart':1002}) tutor = models.ForeignKey(verbose_name='班主任', to='UserInfo',related_name="class_list",limit_choices_to={'depart':1006}) def __str__(self): return "{0}({1}期)".format(self.course.name, self.semester) class Customer(models.Model): """ 客户表 """ qq = models.CharField(verbose_name='qq', max_length=64, unique=True, help_text='QQ号必须唯一') name = models.CharField(verbose_name='学生姓名', max_length=16) gender_choices = ((1, '男'), (2, '女')) gender = models.SmallIntegerField(verbose_name='性别', choices=gender_choices) education_choices = ( (1, '重点大学'), (2, '普通本科'), (3, '独立院校'), (4, '民办本科'), (5, '大专'), (6, '民办专科'), (7, '高中'), (8, '其他') ) education = models.IntegerField(verbose_name='学历', choices=education_choices, blank=True, null=True, ) graduation_school = models.CharField(verbose_name='毕业学校', max_length=64, blank=True, null=True) major = models.CharField(verbose_name='所学专业', max_length=64, blank=True, null=True) experience_choices = [ (1, '在校生'), (2, '应届毕业'), (3, '半年以内'), (4, '半年至一年'), (5, '一年至三年'), (6, '三年至五年'), (7, '五年以上'), ] experience = models.IntegerField(verbose_name='工作经验', blank=True, null=True, choices=experience_choices) work_status_choices = [ (1, '在职'), (2, '无业') ] work_status = models.IntegerField(verbose_name="职业状态", choices=work_status_choices, default=1, blank=True, null=True) company = models.CharField(verbose_name="目前就职公司", max_length=64, blank=True, null=True) salary = models.CharField(verbose_name="当前薪资", max_length=64, blank=True, null=True) source_choices = [ (1, "qq群"), (2, "内部转介绍"), (3, "官方网站"), (4, "百度推广"), (5, "360推广"), (6, "搜狗推广"), (7, "腾讯课堂"), (8, "广点通"), (9, "高校宣讲"), (10, "渠道代理"), (11, "51cto"), (12, "智汇推"), (13, "网盟"), (14, "DSP"), (15, "SEO"), (16, "其它"), ] source = models.SmallIntegerField('客户来源', choices=source_choices, default=1) referral_from = models.ForeignKey( 'self', blank=True, null=True, verbose_name="转介绍自学员", help_text="若此客户是转介绍自内部学员,请在此处选择内部学员姓名", related_name="internal_referral" ) course = models.ManyToManyField(verbose_name="咨询课程", to="Course") status_choices = [ (1, "已报名"), (2, "未报名") ] status = models.IntegerField( verbose_name="状态", choices=status_choices, default=2, help_text=u"选择客户此时的状态" ) consultant = models.ForeignKey(verbose_name="课程顾问", to='UserInfo', related_name='consultanter',limit_choices_to={'depart':1001}) date = models.DateField(verbose_name="咨询日期", auto_now_add=True) recv_date = models.DateField(verbose_name="当前课程顾问的接单日期", null=True) last_consult_date = models.DateField(verbose_name="最后跟进日期", ) def __str__(self): return self.name class ConsultRecord(models.Model): """ 客户跟进记录 """ customer = models.ForeignKey(verbose_name="所咨询客户", to='Customer') consultant = models.ForeignKey(verbose_name="跟踪人", to='UserInfo',limit_choices_to={'depart':1001}) date = models.DateField(verbose_name="跟进日期", auto_now_add=True) note = models.TextField(verbose_name="跟进内容...") def __str__(self): return self.customer.name + ":" + self.consultant.name class Student(models.Model): """ 学生表(已报名) """ customer = models.OneToOneField(verbose_name='客户信息', to='Customer') class_list = models.ManyToManyField(verbose_name="已报班级", to='ClassList', blank=True) emergency_contract = models.CharField(max_length=32, blank=True, null=True, verbose_name='紧急联系人') company = models.CharField(verbose_name='公司', max_length=128, blank=True, null=True) location = models.CharField(max_length=64, verbose_name='所在区域', blank=True, null=True) position = models.CharField(verbose_name='岗位', max_length=64, blank=True, null=True) salary = models.IntegerField(verbose_name='薪资', blank=True, null=True) welfare = models.CharField(verbose_name='福利', max_length=256, blank=True, null=True) date = models.DateField(verbose_name='入职时间', help_text='格式yyyy-mm-dd', blank=True, null=True) memo = models.CharField(verbose_name='备注', max_length=256, blank=True, null=True) def __str__(self): return self.customer.name class ClassStudyRecord(models.Model): """ 上课记录表 (班级记录) """ class_obj = models.ForeignKey(verbose_name="班级", to="ClassList") day_num = models.IntegerField(verbose_name="节次", help_text=u"此处填写第几节课或第几天课程...,必须为数字") teacher = models.ForeignKey(verbose_name="讲师", to='UserInfo',limit_choices_to={'depart':1002}) date = models.DateField(verbose_name="上课日期", auto_now_add=True) course_title = models.CharField(verbose_name='本节课程标题', max_length=64, blank=True, null=True) course_memo = models.TextField(verbose_name='本节课程内容概要', blank=True, null=True) has_homework = models.BooleanField(default=True, verbose_name="本节有作业") homework_title = models.CharField(verbose_name='本节作业标题', max_length=64, blank=True, null=True) homework_memo = models.TextField(verbose_name='作业描述', max_length=500, blank=True, null=True) exam = models.TextField(verbose_name='踩分点', max_length=300, blank=True, null=True) def __str__(self): return "{0} day{1}".format(self.class_obj, self.day_num) class StudentStudyRecord(models.Model): ''' 学生学习记录 ''' classstudyrecord = models.ForeignKey(verbose_name="第几天课程", to="ClassStudyRecord") student = models.ForeignKey(verbose_name="学员", to='Student') record_choices = (('checked', "已签到"), ('vacate', "请假"), ('late', "迟到"), ('noshow', "缺勤"), ('leave_early', "早退"), ) record = models.CharField("上课纪录", choices=record_choices, default="checked", max_length=64) score_choices = ((100, 'A+'), (90, 'A'), (85, 'B+'), (80, 'B'), (70, 'B-'), (60, 'C+'), (50, 'C'), (40, 'C-'), (0, ' D'), (-1, 'N/A'), # 通常情况下-1表示没有或者数据丢失 (-100, 'COPY'), (-1000, 'FAIL'), ) score = models.IntegerField("本节成绩", choices=score_choices, default=-1) homework_note = models.CharField(verbose_name='作业评语', max_length=255, blank=True, null=True) note = models.CharField(verbose_name="备注", max_length=255, blank=True, null=True) homework = models.FileField(verbose_name='作业文件', blank=True, null=True, default=None) stu_memo = models.TextField(verbose_name='学员备注', blank=True, null=True) date = models.DateTimeField(verbose_name='提交作业日期', auto_now_add=True) def __str__(self): return "{0}-{1}".format(self.classstudyrecord, self.student)