One-to-One Association: *一个person只对应一个personal_info *一个personal_info只属于一个person *belongs to用foreign key来链接 rails g model personal_info height:float weight:float person:references 此外你同时也有2个method build_personal_info(hash)#=> 在数据库中创建record create_perso…

The SQLAlchemy Object Relational Mapper presents a method of associating user-defined Python classes with database tables, and instances of those classes (objects) with rows in their corresponding tables. It includes a system that transparently synch…

原文链接:http://www.c-sharpcorner.com/UploadFile/3d39b4/relationship-in-entity-framework-using-code-first-approach-w/ In this article, you will learn about relationships in Entity Framework using the Code First Approach with Fluent API. 在这篇文章中,你将会学习到使用EF…

自引用 public class PictureCategory { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int CategoryId { get; private set; } public string Name { get; set; } public int? ParentCategoryId { get; private set; } public virtual PictureCategory Pa…

命令行: php artisan controller:make UserController This will generate the controller at /app/controller/user.php and user.php. php artisan db:seed --class=AuthorTableSeeder php artisan db:seed,可以执行多个填充类.该方法是执行的DatabaseSeeder这个类 获取已持久化的用户提交的信息: Input::ol…

Let’s learn by example. Throughout this tutorial, we’ll walk you through the creation of a basic poll application. It’ll consist of two parts: A public site that lets people view polls and vote in them. An admin site that lets you add, change and del…

Single Table Inheritance Represents an inheritance hierarchy of classes as a single table that has columns for all the fields of the various classes. These are the strengths of Single Table Inheritance: There's only a single table to worry about on t…

This is a Laravel 4-5 package for working with trees in relational databases. Laravel 5.5, 5.6, 5.7, 5.8 is supported since v4.3 Laravel 5.2, 5.3, 5.4 is supported since v4 Laravel 5.1 is supported in v3 Laravel 4 is supported in v2 Although this pro…

参考:https://msdn.microsoft.com/zh-cn/library/vstudio/bb311040%28v=vs.110%29.aspx 使用 join 子句可以将来自不同源序列并且在对象模型中没有直接关系的元素相关联. 唯一的要求是每个源中的元素需要共享某个可以进行比较以判断是否相等的值. 例如,食品经销商可能具有某种产品的供应商列表以及买主列表. 例如,可以使用 join 子句创建该产品同一指定地区供应商和买主的列表. join 子句接受两个源序列作为输入. 每个序列中…

Quick install guide 1.1   Install Python, it works with Python2.6, 2.7, 3.2, 3.3. All these version of Python include a lightweight database SQLite, so you don't need to setup a database 1.2   Remove any old versions of Django: if you are upgrading y…