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MS SQL creating many-to-many relation with a junction table

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问题 I'm using Microsoft SQL Server Management Studio and while creating a junction table should I create an ID column for the junction table, if so should I also make it the primary key and identity column? Or just keep 2 columns for the tables I'm joining in the many-to-many relation? For example if this would be the many-to many tables: MOVIE Movie_ID Name etc... CATEGORY Category_ID Name etc... Should I make the junction table: MOVIE_CATEGORY_JUNCTION Movie_ID Category_ID Movie_Category

How to configure a One-to-Many relationship in EF

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问题 I have the following model public class PageConfig : Base { // Properties Etc.. public ICollection<Image> ScrollerImages { get; set; } } My approach is to bind using a junction table { PageConfigID, ImageID }. In my model binder i tried the following.. modelBuilder.Entity<PageConfig>() .HasMany(x => x.ScrollerImages) .WithMany() .Map(x => { x.ToTable("junc_PageConfigScrollerImages"); x.MapLeftKey("PageConfigID"); x.MapRightKey("ImageID"); }); Which results in a null collection of images. How

Many to many relationship with junction table in Entity Framework?

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问题 I'm trying to create a many-to-many relationship in Entity Framework (code first), according to the following post: Database design for limited number of choices in MVC and Entity Framework? However, I can't get it to work properly, and I'm sure I'm doing something very simple the wrong way. Here's the diagram I have no from my attempts: The point of the junction table is that I need to have an extra property, Level, in the relationship, so I can't just go with a direct relationship between

How to retrieve the last autoincremented ID from a SQLite table?

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I have a table Messages with columns ID (primary key, autoincrement) and Content (text). I have a table Users with columns username (primary key, text) and Hash. A message is sent by one Sender (user) to many recipients (user) and a recipient (user) can have many messages. I created a table Messages_Recipients with two columns: MessageID (referring to the ID column of the Messages table and Recipient (referring to the username column in the Users table). This table represents the many to many relation between recipients and messages. So, the question I have is this. The ID of a new message

What is the difference between an entity relationship model and a relational model?

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I was only able to find the following two differences: The relationships in an E-R model are explicitly defined, while they are implicit in a relational model. Relational models require an intermediate table (often called a "junction table") to hold two foreign keys that implement the many-to-many relationship. And why do we use the relational model, when we have an E-R diagram ? You have it backwards. The relationships in an E-R model are explicitly defined, while they are implicit in a relational model. No. Each Relational Model (RM) database base table and query result represents an

NHibernate - Many to Many Query using Junction/Joiner Table

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问题 I\'ve found very similar questions here but none that match exactly what I\'m looking for. The two closest threads I\'ve found are (yes, they are different threads): NHibernate many-to-many criteria (1) NHibernate many-to-many criteria (2) However, I think both of those are using direct Many-to-Many relationships. I am actually simulating the Many-to-Many relationship by having two One-to-Many relationships with a junction table, which is pretty standard practice. Here are my NHibernate

What is the difference between an entity relationship model and a relational model?

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问题 I was only able to find the following two differences: The relationships in an E-R model are explicitly defined, while they are implicit in a relational model. Relational models require an intermediate table (often called a \"junction table\") to hold two foreign keys that implement the many-to-many relationship. And why do we use the relational model, when we have an E-R diagram ? 回答1: You have it backwards. The relationships in an E-R model are explicitly defined, while they are implicit in