I have an entity that has a 1-to-many relationship with another ( Entity Position has One Department).
In the details view I'm showing in s combobox a list of all the departments available and I want to start the selecteditem in the combo is the department to which the entity is related.
The problem is than I am using layers so the Position context it is different to the context of the list of departments and when I do something like:
comboBoxDepartments.SelectedItem = Position.Departament
does not work, how can I make a comparison of the items of an entity with a different context?
If the entities have a unique identity, then compare the identity. If there's another unique column (name, for instance) that is NOT NULL, then you could compare that.
Otherwise, see https://stackoverflow.com/search?q=Compare+2+Entities.
Related
I have searched on the net but was not able to get an answer for my case. I am migrating a project on doctrine.
What is the correct way to link an entity to another entity that contains all the "families" of a project.
The families can be for instance :
"project_status" : status1, status2, status3
"countries" : en, us, cn ...
"tags" : tag1, tag2, ...
So all these values are stored in the same table in database and my entity handle this.
So now i have an entity that can have for example several countries or tags.
In the database i have one text field for the countries and one text field for the tags. And i store the ids of each tag or family inside these fields.
So let's say that I have one entity called "family" and one entity called "myEntity".
What is the best way to do ?
Ok maybe I have found one way in fact.
Instead of using my usual text field in my entity table to store the ids of the families I will use a join table.
So let's say that I have one table with my different lists in my project (country, file_status, and other possible lists). I will then have one entity for this table "familyEntity".
I will create a table that will be used for the cases in which one entityA can have several values of the same family (country for instance). In that case, I wil have a many to many association between familyEntity and entityA for that family.
If I have another entityB that uses the family "status" with several values possible, I will also have a many to many association using the same table for the association.
In the other cases in which only one value is possible for one family I will have many to one association.
Don't know if it is the right way but it occured to me that way. This solution seems ok for primary keys that are not compound).
I have an app that houses product data via a Product model and table. Each product has specific state availability (multiple states) that I will need to filter and/or search by in the future. I am hoping to find someone who can tell me the most efficient way to store this data. As I see it, I have two options.
The first is to simply create 50 columns in my table, titled with each state name and containing a boolean value. I can then simply filter by = "avail in California" if product.ca. While this certainly works, it seems a bit cumbersome, especially when searching for multiple state availability.
The second option would be to simply have one column("states") that stores an array of available states and then filter by = "avail in California" if product.states.include? "CA". This seems like a better solution for two reasons. The first, it just allows for a cleaner DB table. Second, and more important, I can allow my user to search by simply saving the user's input as a variable(user_input) and then = "avail in California" if product.states.include? user_input. This solution does call for a little more work up front however when saving the product in the DB, since I won't be able to simply check off a boolean value.
I think option two makes the most sense, but am hoping for some advice as to why or why not. I have found a few similar questions, but they do not seem to explain which solution would be better, just how to accomplish each.
What should I do?
You should normalize unless you have a really good reason not to, and I don't see one in your overview.
To normalize, you should have the following tables:
product table, one record per product
state table, one record per state
product_state table, one entry for every product that is in a state
The product_state schema looks like this:
(product_state_id PK, product_id FK, state_id FK)
UNIQUE INDEX(product_id,state_id);
This allows you to have a product in zero or more states.
I assume that since you’re selling products, you will be charging taxes. There are different taxes by state, county, city. There are country taxes in some countries too.
So you need to abstract these entities into a common parent, usually called GeopoliticalArea, so that you can point a single foreign key (from, say, a tax rates table) at any subtype.
create table geopolitical_area (
id bigint primary key,
type text not null
);
create table country (
id bigint primary key references geopolitical_area(id),
name text not null unique
);
-- represents states/provinces:
create table region (
id bigint primary key references geopolitical_area(id),
name text not null,
country_id bigint references country(id),
unique (name, country_id)
);
insert into geopolitical_area values
(1, 'Country'),
(2, 'Region');
insert into country values
(1, 'United States of America');
insert into region values
(2, 'Alabama', 1);
As indicated in the Entity Framework image below, I have 3 tables, tblModel, tblModelFetish and tblFetish. A record in tblModel can have multiple records in the tblModelFetish table linked by the modelid column. The tblModelFetish table links to the tblFetish table via the fetishID column to get the fetish description stored in the fetish column. This Entity Model was generated with VS 2010 from an existing database including foreign keys.
a Entity Data Model http://spreadthenudes.com/efmodel.jpg
Using the odata syntax, I'm able to access all models (http://localhost:51157/WcfDataService.svc/tblModels) or a specific model (http://localhost:51157/WcfDataService.svc/tblModels(11)) successfully. I'm having trouble accessing the related tables data via odata, I've tried many permutations including expand etc.
What I want is a result set of all the columns in the tblModel and the related tblFetish records including the fetish column from the tblFetish table. In other words, Mary (a modelname in tableModel) has 3 fetishes (3 records in tblModelFetish) named beach, travel and coffee (stored in tblFetish, fetish column).
What is the odata syntax to acquire this?
thanks for reading! Bob
Try either:
http://localhost:51157/WcfDataService.svc/tblModels(11)?$expand=tblModelFetishes/tblFetish
or
http://localhost:51157/WcfDataService.svc/tblModels?$filter=id eq 11&$expand=tblModelFetishes/tblFetish
Just to make it clear you will not get one huge result set with all columns but the entity graph consisted of your entities.
Can anyone advise on the best way to create a UI for establishing Many-to-Many relationships ?
Lets use an example from a previous question List <<-->> Patient.
I can create two separate Table Views, one for Lists and another for Patients which will allow the user to create Lists and Patients using two separately created Array Controllers (Lists and Patients), one linked to the List entity and other linked to the Patient entity.
Now I would like to be able to add/remove Patients from a List by creating an Table View that shows only Patients in the selected List. To do this I create a Array Controller (ListPatients) linked to the entity Patient with a Content Set binding to Lists.selection.patients.
Now things stop working nicely from here on....
If I bind a button to the ListPatients.add method then a NEW Patient gets created - there seems to be no way to simply add a NEW relationship between an existing Patient and the List.
Ideally what I would like to be able to do is to have a drop down list to select the Patient from.
Does anyone have any suggestions as to how best to do this without needing to create a new entity to represent this relationship.
What you need is a swapping Master-Detail view where either the List table or the Patient table is the Master or the Detail at any particular time.
When the List is the Master view, selecting a row will cause the Detail view to display all the Patient objects in the rowList.patients relationship. When the Patient is the Master view, selecting a row will cause the Detail view to display all the List objects in the rowPatient.lists relationship.
You really do want to break up the UI so the users always have a clear idea what the relationship is between the two tables. I would recommend a set of four tables, two each for each Master-Detail setup. That way, the user will also understand what they are looking at.
That will also make it easy to add new objects. Just put an add new button under the detail table and the user will understand that clicking it will add a new object to the relationship of the object selected in the Master view.
I have an entity (e.g. Employee) in a managed object model that is related to two other entities (e.g. Department and Team). Both relationships are one-to-many (i.e. an Employee must have one Department and one Team, Teams and Departments have many Employees). The two may or may not overlap (e.g. a team might be made up of employees from HR, Accounting & I.T. or it might jut consist of several employees from the one department).
Department <-->> Employee <<--> Team
I have two NSArrayControllers providing data for two NSTableViews, a Department table and a Team table. Employees can move between departments and between teams without any problems but I'm not sure how to delete (fire) the employee.
If I send either of the array controllers a remove message the employee is taken out of the team (for example) but left in the department and the object graph is in an inconsistent state. Even if I call the remove action on both controllers the object is not deleted - it is orphaned and just hangs around in limbo.
Originally I had the Department & Team relationships (of the Employee entity) set to a delete rule of Nullify but even changing one or both to cascade doesn't help.
Do I need to override the remove: action on the array controllers to actually delete the employee or am I missing something really obvious?
The NSArrayController has two different behaviors when you're using Core Data. If it is configured to simply fetch objects directly from the managed object context, it will delete the objects when they are removed.
If you're binding the contentSet to another controller, like it sounds like you are in this case, the default behavior is to simply remove the object from the relationship. If you want to delete it, though, there is a "deletes object on remove" binding option, which will produce the result you want.