I want to create a table which stores customer's addresses for a servicing company.
Some customers have a home address, while others have ana apartment, and service contracts include whole complex service contract.
How can I approach this design without redundency in apartment complex based addresses where only the flat number is different.
It is worth it to make a Many to Many kind of reference between two tables? e.g. : tblCustomer, tblAddressdetails, tblAddressUnit.
Related
I'm trying to find out a way to find the relations of a specific entity, say one targeted for deletion.
Example setup:
Country entity can have many Currencies.
Currency entity can have Countries.
A Country may have a primary Currency.
Therefore, the setup is: Country <-> (1-n) <-> CountryCurrency <-> (n-1) <-> Currency.
In the above example it's easy to find if a Country, targeted for deletion, has any associated Currencies.
However, imagine that the above is setup in a global kind of way and usable for other modules within the application.
If another module, Address for example, used a Country in a uni-directional relationship (an Address has one Country): how can I figure out that the specific Country entity may not be deleted without trying to and thus receiving a Foreign Key constraint error?
I'm hoping that Doctrine has something for this built in, but haven't been able to find it in the documentation. Have been Google'ing it for a while now as well without success. Always in the trend of: "well, you just $entity->getSomeRelation()->count() > 0 and you know", but I'm looking for a generic solution/method that can apply to any entity.
There is no generic solution for it because it always depends on your business model.
Deleting entity with relation can lead to different scenarios:
deleting related entities as well
setting the relation to null
or disallow deleting at all.
So it's up to you to do the check mannualy, depending on your case.
I've read through a bunch of tutorials to the best of my ability, but I'm still stumped on how to handle my current application. I just can't quite grasp it.
My application is simply a read-only directory that lists employees by their company, department, or sorted in alphabetical order.
I am pulling down JSON data in the form of:
Employee
Company name
Department name
First name
Last name
Job title
Phone number
Company
Company name
Department
Company name
Department name
As you can see, the information here is pretty redundant. I do not have control over the API and it will remain structured this way. I should also add that not every employee has a department, and not every company has departments.
I need to store this data, so that it persists. I have chosen Core Data to do this (which I'm assuming was the right move), but I do not know how to structure the model in this instance. I should add that I'm very new to databases.
This leads me to some questions:
Every example I've seen online uses relationships so that the information can be updated appropriately upon deletion of an object - this will not be the case here since this is read-only. Do I even need relationships for this case then? These 3 sets of objects are obviously related, so I am just assuming that I should structure it this way. If it is still advised to create relationships, then what do I gain out of creating those relationships in a read-only application? (For instance, does it make searching my data easier and cleaner? etc.)
The tutorials I've looked at don't seem to have all of this redundant data. As you can see, "company name" appears as a property in each set of objects. If it would be advised that I create relationships amongst my entities (which are Employee, Company, Department), can someone show me how this should look so that I may get an idea of what to do? (This is of course assuming that I should use relationships in my model.)
And I would imagine that this would be the set of rules:
Each company has many or no departments
Each department has 1 or many employees
Each employee has 1 company and 1 (or no) department
Please let me know if I'm on the right track here. If you need clarification, I will try my best.
Yes, use relationships. Make them bi-directional.
The redundant information in your feed doesn't matter, ignore it. If you received partial data it could be used to build the relationships, but you don't need to use it.
You say this data comes from an API, so it isn't read-only as far as the app is concerned. Worry more about how you're going to use the data in the app than how it comes from the server when designing your data model.
If models in Master Data Services are representations of subject areas (such as customer, product, etc.), is it possible to have a domain-based attribute that uses a different model as it's source?
For example, if creating a customer model and defining an entity called Customers, this entity will have address information for the customer. City, State/Province, Country, etc.
But rather than creating an entity for CustomerCountry, can I use a Geography model that contains a Country entity and link to that? Then I can also use the Geography.Country entity for Vendors and Employees.
No, you cannot cross model boundaries - the primary reason is that a model is the unit of versioning. There are two workarounds:
Duplicate the entities in question - i.e. copy the geography entities into your customer model
Reference an entity by code - i.e. add a CITY_CODE to your customer entity
Neither of these are great options 1) is unwieldy and 2) doesn't maintain automatic integrity.
Personally I use option 2) where I can with some additional logic/business rules outside of MDS to ensure that codes match. This is easier with codes that are global and do not change such as country and city codes.
This seems quite old but this is now possible in 2016 and is accomplished though Entity Synch. The idea is you can synch your entity across models. There are two ways to run the synch, either on demand or automatically.
See https://learn.microsoft.com/en-us/sql/master-data-services/entity-sync-relationship-master-data-services for more details
I am trying to do something fairly easy to understand with WCF data services, but can't find how to do it.
I have 3 table, Customer, Product and a joint table Customer_Product linking the two other tables (a basic n to n relationship):
Customer <= Customer_Product => Product
I want to get a customer and its products in the same query, so I would like to do something like:
/Service.svc/Customers(23)?$expand=Products
But it tells me that there is no Products navigation property on the table Customer.
The only option that I found is to do:
/Service.svc/Customers(23)?$expand=Customer_Product
and then make another call to get the Product details.
Is there a clean way to do this?
Thanks a lot in advance.
The many to many relationships are usually modeled by the service by hiding the join table (if the only thing it stores is the relationship and there's no data in it). If you're using EF in the service this should be pretty easy to do.
If you do need to expose the join table for some reason, then you can issue a query like:
/Service.svc/Customers(23)?$expand=Customer_Product/Product
(expands can be multiple levels deep). Of course reading the results will be a bit more complicated because of the two levels there, but you do get the data you need.
I am trying to draw a domain model or class diagram in UML for car dealership. I am stuck with how to present test drive in the model. One way is to have appointment class and then test-drive as sub class. A dealer also offers after-sale vehicle service so i could have appointment/booking class as super class and then vehicle service and test-drive as two sub classes.
Another way is to have the customer class have a direct relationship with test drive class and vehicle service class under appointment class.
A dealer also sells new and used cars and their parts.
A dealer also offers finance for car sale.
Would testdrive class have relationship with vehicle class or there is separate class for display and testdrive class?
Another question is how do I show potential customers and their inquiries about sale and service in the model. A dealer wants to save details of potential customers if they allow for marketing purposes. Shall I have two classes: one for customers and one for potential customers or it can be achieved just by using an attribute in customer class?
You can really only distinguish the right decision by having a good set of use cases or expected behaviors of the model.
This will inform whether a particular sub-classing is really accurate.
I can see that an appointment might contain several test-drives, which are themselves linked to individual vehicles, So a test-drive itself is nothing more than a link from a customer to a vehicle which are linked to an appointment.
test-drive would contain the information relevant only to the test-drive:
reference to the customer - even this might be debatable to include
reference to the vehicle
length of test drive
location (perhaps the vehicle was driven at a different location than could be determined from the owning appointment)
customer temperature (hot or cold - i.e. did the customer seem enthusiastic)
comments
etc.
But what is not in the test-drive object is anything related to the appointment - since it is always contained in a collection - possibly as part of an appointment or some other event container. Now if the containers which can contain test-drives always include customer information, I might not even include the customer reference in the test-drive object - after all, it will be redundant.
It depends if test-drives can occur in non-appointment scenarios - perhaps at a "sales event" or an "open house" or something where appointments are not actually created in the use cases - or if test-drives for multiple customers will occur within a container.
The second part of your question has been forgotten (easily done when you ask two questions in one):
Another question is how do I show potential customers and their inquiries about sale and service in the model. A dealer wants to save details of potential customers if they allow for marketing purposes. Shall I have two classes: one for customers and one for potential customers or it can be achieved just by using an attribute in customer class?
I think your use case there is "A dealer wants to save details of potential customers if they allow for marketing purposes." and the simplest solution is to have a Mailing List collection which holds name and address of each potential customer.
I think you miss the point. The aim of the domain model is make famliiar you with the domain:
-- What kind of entities you have in yor domain?
-- If they are important for your system under desing,
what kind of properties they have, how they behave?
-- What kind of business rules they obey?
The rest is details. Think like a map maker. Record what there is.Create a simple map so you can not lost your way in that domain. Not try to invent.Abstract what exist in the domain: Not run behind the "fancy abstractions" you created yourself.
Domain model can be used as a source
for object oriented analysis/design.
But their aim is not to represent
software abstractions.