Web框架开发-Django模型层(数据库操作）

一、ORM介绍

• MVC或者MVC框架中包括一个重要的部分，就是ORM，它实现了数据模型与数据库的解耦，即数据模型的设计不需要依赖于特定的数据库，通过简单的配置就可以轻松更换数据库，这极大的减轻了开发人员的工作量，不需要面对因数据库变更而导致的无效劳动
• ORM是“对象-关系-映射”的简称。

映射关系：

表名 --------------------》类名

　　字段--------------------》属性

　　表记录-----------------》类实例化对象

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#sql中的表                                                       #创建表:      CREATE TABLE employee(                                                     id INT PRIMARY KEY auto_increment ,                                    name VARCHAR (20),                                                      gender BIT default 1,                                                  birthday DATA ,                                                         department VARCHAR (20),                                                salary DECIMAL (8,2) unsigned,                                        );   #sql中的表纪录                                                    #添加一条表纪录:                                                                INSERT employee (name,gender,birthday,salary,department)                         VALUES   ("alex",1,"1985-12-12",8000,"保洁部");                 #查询一条表纪录:                                                                 SELECT * FROM employee WHERE age=24;                                 #更新一条表纪录:                                                                 UPDATE employee SET birthday="1989-10-24" WHERE id=1;                #删除一条表纪录:                                                                DELETE FROM employee WHERE name="alex"                             #python的类 class Employee(models.Model):      id=models.AutoField(primary_key=True)      name=models.CharField(max_length=32)      gender=models.BooleanField()      birthday=models.DateField()      department=models.CharField(max_length=32)      salary