I have 3 tables, one is called Users, one is called Categories and one is a linking table called User_Categories_Map to link users to categories in a many-to-many relationship. The linking table consists of UserId's and CategoryId's. After generating the subsonic classes, I would assume I'd be able to then type User.singleOrDefault(x => x.ID == 1).Categories to select all the categories for a user. However, this doesn't work. If you can understand what I'm trying to accomplish here, can anyone tell me how I can make this work in subsonic? Consequently, I cannot find any documentation on subsonic. Subsonicproject.com only has a short page a few articles about how to set it up. Is there documentation somewhere for subsonic?
int lUserID =1; // suppose 1 is Id of user
CategoriesCollection lCategories = DB.Select().From<Categories>()
.InnerJoin(User_Categories_Map)
.InnerJoin(Users)
.Where(Users.Columns.Id).IsEqualTo(lUserID)
.ExecuteAsCollection<CategoriesCollection>();
It will return collection of categories associated to a specific user..
Related
I have users for my website that need to log in. In order to do that, I have to check the database for them, by email address or a hash of their email.
Some of my users have an online course in common.
Others are all on the same project.
There are multiple projects and courses.
How might I set up my table so that I can grab individual users, and efficiently query related groups of users?
I'm thinking...
PK = user#mysite
SK = user#email.com
projects = [1,2,3]
courses = [101,202,303]
I can get any user user with a get PK = user#mysite, SK = user#email.com.
But if I query, I have to filter two attributes, and I feel like I'm no longer very efficient.
If I set up users like this on the other hand:
PK = user#email.com
SK = 1#2#3#101#202#303
projects = [1,2,3]
courses = [101,202,303]
Then I can get PK = user#gmail.com and that's unique on its own.
And I can query SK contains 101 for example if I want all the 101 course students.
But I have to maintain this weird # deliminated list of things in the SK string.
Am I thinking about this the right way?
You want to find items which possess a value in an attribute holding a list of values. So do I sometimes! But there is not an index for that.
You can, however, solve this by adding new items to the table.
Your main item would have the email address as both the PK and the SK. It includes attributes listing the courses and projects, and all the other metadata about that user.
For each course, you insert additional items where the course id is the PK and the member emails are the various SKs in that item collection. Same for projects.
Given an email, you can find all about them with a get item. Given a course or project you can find all matching emails with a query against the course or project id. Do a batch get items then if you need all the data about each email.
When someone adds or drops a course or project, you update the main item as well as add/remove the additional indexed items.
Should you want to query by course X and project Y you can pull the matching results to the client and join in the client on email address.
In one of your designs you're proposing a contains against the SK, which is not a supported operator against SKs so that design wouldn't work.
I am building a social website and I am laying out how the feed will work. I want to use the answer here: How to implement the activity stream in a social network and implement the database design mentioned:
id
user_id (int)
activity_type (tinyint)
source_id (int)
parent_id (int)
parent_type (tinyint)
time (datetime but a smaller type like int would be better)
The problem is I don't know how I would map the source_id based off activity_type. If a user registers, I want the source_id to be the user that registered. If someone creates a group the source_id will be the group. I know I can just use simple IDs without keys I just wanted to know if Symfony had some sort of way to do this built in.
If I fetch the feed and the activity_type is user_register I would like to be able to do this to get the source (user) without running an additional query:
$feedEntity->getSource()->getUsername(); //getSource() being the User entity
And if the source_typeis "user_post":
$feedEntity->getSource()->getMessage(); //getSource() being the UserPost entity
I basically just want to find the best way to store this data and make it the fastest.
Not easy to deal with doctrine and i think it cannot achieved 100% automatically
However, the keyword is table inheritance
http://docs.doctrine-project.org/en/2.0.x/reference/inheritance-mapping.html#single-table-inheritance
I think you could achieve your goal by doing something like this :
You create a discriminator map by the type column of the table which tells doctrine to load this entity a UserSource (for example)
This UserSource can be an own entity (can be inherited from a base class if you want) where you can decide to map the source_id column to the real User Entity
You can use instanceof matching against the namespace of the different entities mapped inside your discriminator map to define different behaviours for the different sources
I have an application built with entity framework 5 code first, where I'm using code first against an existing database. I have two entities, Foo and Bar, which are connected through a many to many relationship using a table in sql server with foreign key to each of the two tables. In code, the two entity types each have a collection of the other, and in the dbcontext they are mapped together like this:
modelBuilder.Entity<Foo>()
.HasMany(e => e.Bars)
.WithMany(s => s.Foos)
.Map(l =>
{
l.ToTable("FooBar");
l.MapLeftKey("FooId");
l.MapRightKey("BarId");
}
);
The problem is that I can add relationship between the entities by adding eachother to their collections and saving, however when I do the opposite, removing eachother from their collections, the record in the relationship table are not being removed.
I ended up just importing the bridge table in the model. If anyone knows how this is supposed to work, please leave an answer here.
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 Consultant and Program. I added the ConsultantProgramLink entity manually in the designer, and then added associations to Program and Consultant respectively, selecting to add a FK for each, and then made them both primary keys. But when I do it like this it doesn't work as I expected:
If I had done a direct association between Consultant and Program, I would have been able to refer to, say, Consultant.Programs in my code. But that doesn't work now with the junction table. Is there any way to remedy this, or do I always have to go through the junction property (Consultant.ConsultantProgramLink.Programs)? In any case, even if I do try to go through the junction property it doesn't help. I can do Consultant.ConsultantProgramLink in my code, but another dot doesn't give me the navigation property Programs (which for some reason also became simply Program, why? Can I just rename them if I eventually get access to them at all?).
So what am I doing wrong? Why can't I access the properties through dot notation in my code?
Once you model a junction table as an entity you indeed lose direct many-to-many relation between Consultant and Program. That is how it works. You will either have direct many-to-many relation or additional properties in the junction table. Not both. If you want both you can try creating custom Programs property on Consultant and use linq query to get related programs:
public IEnumerable<Program> Programs
{
get
{
return this.ConsultantProgramLinks.Select(l => l.Program);
}
}
The example is also the explanation of your last problem. You can't have Program property on ConsultantProgramLink because it is a collection of related entities, not single entity (it should be called ConsultantProgramLinks). The property in ConsultantProgramLink entity is called simply Programbecause it represents single entity not collection.
Edit:
If you need each Program to be automatically associated with each Consultant you must enforce it when you are going to create new Program. Having junction table exposed as separate entity will probably allow you achieving it easily:
var program = new Program();
...
context.Programs.AddObject(program);
var ids = from c in context.Consultants
select c.Id;
foreach (var id in ids)
{
var link = new ConsultantProgramLink
{
ConsultantId = id,
Program = program
};
context.ConsultantProgramLinks.AddObject(link);
}
context.SaveChanges();
If you add new Consultant you will have to create links to all programs in the same way.
The disadvantage is that if you have for example 1000 consultants this construct will create 1001 database inserts where each insert will be executed in separate roundtrip to the database. To avoid it the only option is either use stored procedur or trigger on Program table.
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.