In the Module Builder, let's say I want to add custom modules Pets and Visits for my pet grooming salon.
If I want to be able to access Visits from a logic hook in the Pets module, and also Pets from Visits, and I also want to show each one as a panel in the other, should I:
Define a Many-to-One relationship from Visits (L) to Pets (R)?
Define a One-to-Many relationship from Pets (L) to Visits (R)?
Both?
I don't know if the answer's the same for Sugar; I think there might be a different "module builder" sort of thing for it.
As far as Sugar is concerned you'd want a many-to-many relationship if you want a panel in both modules.
However if you want to limit the relationship to a maximum of one Pet per Visit, then a one-to-many relationship is appropriate with Pet as primary module (L) and Visits as related Module (R).
Please note that in Visits the related Pet will possibly not be displayed as panel but as a relate field for such a relationship (at least in EditView, in Record View it probably is still displayed as Panel in SuiteCRM as it uses the old UI of Sugar).
Either way a relationship can always be accessed from both sides, so you don't need a second relationship)
Further info: https://support.sugarcrm.com/Knowledge_Base/Studio_and_Module_Builder/Understanding_Relationship_Creation_Options/
PS: If you want a one-to-many relationship but a panel even on the side where only one record of the other module can be linked to most at any time, then you can probably achieve this by creating a many-to-many relationship first and adjust the relationship's metadata to have true_relationship_type as one-to-many in code.
Related
I work in cattle production and I am learning about database design with postgreSQL. Now I am working on an entity attribute relationship model for a database that allows to register the allocation of the pastures in which cattle graze. In the logic of this business an animal can be assigned to several grazing groups during its life. Each grazing group in turn has a duration and is composed of several pastures in which the animals graze according to a rotation calendar. In this way, at a specific time, animals graze in a pasture that is part of a grazing group.
I have a situation in which many grazing groups can be assigned to many animals as well as many pastures. Trying to model this problem I find a fan trap because there are two one-to-many relationships for a single table. According to this, I would like to ask you about how one can deal with this type of relationship in which one entity relates to two others in the form of many-to-many relationships.
I put a diagram on the problem.
model diagram
Thanks
Traditionally, using a link table (the ones you call assignment) between two tables has been the right way to do many-to-many relationships. Other choices include having an ARRAY of animal ids in grazing group, using JSONB fields etc. Those might prove to be problematic later, so I'd recommend going the old way.
If you want to keep track of history, you can add an active boolean field (to the link table probably) to indicate which assignment is current or have a start date and end date for each assignment. This also makes it possible to plan future assignments. To make things easier, make VIEWs showing only current assignment and further VIEWs to show JOINed tables.
Since there's no clear question in your post, I'd just say you are going the right way.
I'm a bit confused about this naming convention.
What is the difference between them and are target/source interchangeable with owning/not owning?
One thing in particular is hard to understand:
"The main difference between a OneToOne and a ManyToOne relationship in JPA is that a ManyToOne always contains a foreign key from the source object's table to the target object's table, where as a OneToOne relationship the foreign key may either be in the source object's table or the target object's table"
JPA wikibooks
I can't imagine such situation in uni one-to-one
Differences between them are a little confusing. You should practice a lot to understand very well.
At first, you should understand some terminology:
Role : In every relationship there are two entities that are related to one another, and each entity is said to play a role in the relationship.
Direction : Relationships can be unidirectional or bidirectional. For e.g.. a Person has an address is normally unidirectional whereas Employee working on a project is normally bidirectional. We will look at how to identify and define directionality while coming up with a Data Model.
In order to have relationships at all, there has to be a way to create, remove, and maintain them. The basic way this is done is by an entity having a relationship attribute that refers to its related entity in a way that identifies it as playing the other role of the relationship. It is often the case that the other entity, in turn, has an attribute that points back to the original entity. When each entity points to the other, the relationship is bidirectional. If only one entity has a pointer to the other, the relationship is said to be unidirectional. A relationship from an Employee to the Project that they work on would be bidirectional. The Employee should know its Project, and the Project should point to the Employee working on it. A UML model of this relationship is shown here. The arrows going in both directions indicate the bidirectionality of the relationship (Form this book >> Pro JPA 2)
Then dive into this link (archived from the original)
I'd like to comment only the links, but I need 50 reputation
If I have two entities; Foo and Bar. And Foo has two properties; bar1 and bar2 of type Bar. Now does Foo have a one-to-many releationship to Bar? At least should it be modeled as that in Core Data? Or is it two one-to-one releationship? How do I set that up properly in Core Data with inverse? The one-to-many releationship I understand but not the last releationship type? Is that even possible or good way to that?
And Foo has two properties; bar1 and bar2 of type Bar. Now does Foo
have a one-to-many releationship to Bar?
No, Foo has two relationships with Bar, and those relationships are named bar1 and bar2. Whether they're "to-one" or "to-many" depends on how you specified them. Select each in the model and see whether the "to-many" checkbox is checked.
At least should it be modeled as that in Core Data?
That depends on what you're trying to model. Do you want to have two separate relationships to specific object (that'd be two different "to-one" relationships), or do you want a single relationship to a group of objects (one "to-many" relationships)? Here's an example that might help clarify things...
A business may have zero or more employees. A business also has a single chief executive officer and a single chairman of the board. So the Business entity might have a "to-many" relationship named employees with the Person entity. It might also have "to-one" relationships named ceo and chairman, again with Person. Those might not be strictly necessary -- maybe the CEO and Chairman are both employees, so you could find them by searching the set of employees and filtering by job title. But it can be handy to have them as separate relationships if you're going to use them often and don't want to have to search through thousands of other employees every time you do.
How do I set that up properly in Core Data with inverse?
Again, it'll depend on what you're modeling. For example, the inverse of the employees relationship would be Person's employer "to-one" relationship.
Entities have several different kind of properties, they have attributes and relationships (and fetched properties, but that's beside the point). It sounds like Foo and Bar are two classes you created with Foo having Bar properties. Then you want assimilate those as Entities in a Core Data model.
Typically, things are done the other way around. You create Entities in the Core Data model editor. You then link the entities by creating relationships. If you add a relationship from Foo to Bar, then it is good practice to create an inverse relationship from Bar to Foo.
Create the relationship from Foo to Bar
Create the relationship from Bar to Foo
Select that last relationship and set its inverse to the first one
Now if you want Xcode to generate the matching NSManagedObject subclasses Foo and Bar, then you can select the Entities and in the Xcode Editor menu, select "Create NSManagedObject subclasses"
You'll then see you're two classes with the proper attributes to match how your model is set up.
I've authored a book on Core Data that explains all this is much deeper details.
This is two one-to-one releationship.
To make inverse just select you entity in inverse field (When you create relation).
I want to create a one to many relationship. My setup is something like:
I have the Profile Entity,
I have the Time entity.
Every profile has a relationship to Time.
How can I define relationships, and add multiple Time entities to a single profile?
I bet it is obvious, but I can't see how to implement.
edit after posting the answer I saw your comment - to define a to-many relationship in the modeller, select the relationship and choose to-many from the options:
To populate the relationship, you can do it two ways. I am assuming your Profile entity has a to-many relationship called times and the inverse relationship is a to-one relationship called profile.
Set the profile on each Time entity as you are creating them. This will automatically populate the inverse relationship (i.e. add the Time to the times set of the profile).
Collect the relevant Time entities in a set and set the times property to this set. Again, the inverse will be automatically populated.
There is more information here. Accessor methods to add individual entities to a to-many relationship can be generated from the managed object model editor in Xcode.
I have the following database structure:
Children --> Gifts <-- Possible_gifts, where the arrow denotes 1-to-many relationship, i.e. "Each child can have many gifts and each one of those gifts is one of the Possible_gifts." (forming the classical many-to-many relationship). Possible_gifts table includes (among other things) the names of the gifts, the Gifts table only has the ID of the Possible_gift, the ID of the child and some other necessary data (like date, etc.)
Now in the Silverlight client I need to get not only the Child and Gift data from the domain service, but also the Possible_gifts table data (mainly the name of each Gift that is associated with the selected Child). I tried:
return this.ObjectContext.Children.Include("Gifts").Include("Gifts.Possible_gifts") as suggested somewhere else, but it doesn't work.
Does anybody have an idea how to solve this?
Thanks.
Discovered where the problem was. I was missing an [Include] attribute in the metadata class of the domain service. It turns out that having the above mentioned code in the domain service alone doesn't do the trick!