I have an entity data model with two entities. One entity called Posts contains blog posts and another entity called Comment contains comments. I set up the association as a one to many relationship and the primary keys are both postid in both Posts and Comment.
However, when I try to bind this to an entitydatasource control it only lets me select either the Posts or the Comment entity set not both. What I want to do is to be able to bind the post with its comments to the data source, but I can't seem to figure out a way to do this.
Any help would be appreciated!
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I have entities "Article" and "Product". Now I want to add comments to these 2 entities. Should I create 2 different entities "ArticleComment" and "ProductComment" with the same properties, and build a ManyToOne relation to their respective entity, or create a single "Comment" entity and find a way to build a relation to both "Article" and "Product" entities. Considering solution #2, how could I do that ?
Considering solution #2, how could I do that ?
One way would be to use Single Table Inheritance
Single Table Inheritance is an inheritance mapping strategy where all classes of a hierarchy are mapped to a single database table. In order to distinguish which row represents which type in the hierarchy a so-called discriminator column is used.
This means that you can easily create two separate entities ArticleComment and ProductComment both extending Comment. Then you use the advantages DiscriminatorMap column provides.
Your Comment entity could hold a relation called parent for instance that would refer to either your Article or Product entities. By creating new instance of ArticleComment or ProductComment your discriminator map field would be automatically populated depending on which type you're using.
This would also give you advantages with using DQL to query related comments by their type. Example from documentation:
$query = $em->createQuery('SELECT u FROM Doctrine\Tests\Models\Company\CompanyPerson u WHERE u INSTANCE OF Doctrine\Tests\Models\Company\CompanyEmployee');
And more. You can read that chapter here. Of course this is just a sample and you can use completely different approach.
I am facing problem in drupal views.
In my view display table having relationship with other entity type.
I am not getting desire output. It show duplicate rows with same title due to entity relationship.
I wanted to aggregate entity relationship field with ",".
I already try some module like : view distinct, views_merge_rows.
But did not work for me.
Please suggest some module.
Have a look at Views Calc and if you cant do it in the database Views Aggregator Plus gives you even more options.
In the business logic we map, Tables to Objects and fields of this table to properties.
What to do in one-to many relationship? Just an example: I have Table, Products and Categories.
I need to drag all products and instead of Category_ID (Products table) need to display actual Category name wich is stored in Category table.
What is propal way of doing it? In similar situations?
You can have a property on the Products Entity that is of type Category Entity. Check this link out from the EntitySpaces (an ORM for .Net) documentation for ideas:
link text
Also, you may want to look into using an ORM.
Either use an ORM like LINQ to SQL or ADO.NET Entity Framework or strongly-typed datasets. But if you want to custom code your business layer, your Category class could have a Products collection property which contains those products, loaded from the DB, which you could infer the name.
HTH.
I am still trying to learn NHibernate best practices, so please be easy on me... :-)
I have a Product class with a Many-To-One relationship set up to a Category class. On my Add A Product page, I am loading a DropDownList with the Categories. Now when the user enters the product information and clicks submit, I have to pull down the Category by ID (DropDownList SelectedValue) from the database to populate the Category property of my Product object so I can save it.
It seems like the Category by ID lookup is a waste. Is there a way I can simply use the ID value that was retrieved from the DropDownList?
Thanks for any advice!
Use ISession.Load() to create a proxy object. eg:
myProduct.Category = session.Load<Category>(userSuppliedCategoryId);
Note that the Load() method doesn't actually hit the database unless you try accessing a property besides the primary key, so there is no extra DB hit.
Ayende has a good post about this
I have created my Database which has:
Artist, tracks and TracksPerArtists
I can do sql queries through the entity model. For example when I make:
database.TRACK.ToList()
I get the list of track to be shown on index view for example. But my foreign keys come empty. While there is an artist and a track, and the correct row for ArtistsPerTrack, this item in my track.ToList() collection is empty.
Is there a different way to fetch those data?
I came from cakePHP framework in which you can define the Model.recursive property to declare the depth of the relations you want to fetch.
Is there anything similar here?
There is something similar.
If "database" is DataContext and Artist and Tracks have many to many relationship in database, you can fetch related entities using Include clause:
database.TRACK.Include("Artists").ToList()
where "Artists" is the name of property on Track entity.