I have a Silverlight 4.0 application that has a normalised database. In this database i have tables for Applicants, Licences, LicenceClasses, LicenceTypes and LicenceStatuses amongst others. The last 3 mentioned tables are lookup tables linked to the Licences table through foreign key relationships.I am using RIA services with the Entity Framework for data access. The scenario i am facing is as follows.
When i create a datagrid on my form i get all the appropriate colums with fields from the Licences table. I want to display the names from the lookup tables that are represented by the ID fields in the Licence table. I need to show for instance the LicenceStatus instead of the LicenceStatusID.
I have followed some examples about including the related collections in my domain service and making all the appropriate Include annotations in the Metadata classes. While i can correctly get this to work with one lookup field , i can't seem to find a way to include more than one look up table in my GetLicences query.
public IQueryable<LearnersLicence> GetLearnersLicences()
{
return this.ObjectContext.LearnersLicences.Include("LicenceClass");
}
In the above query i can only include the LicenceClass collection and i have found no way of including the LicenceStatus collection or multiple look up collections that i need to display.
How do i go about accomplishing this
You can include multiple tables by adding a include for each.
public IQueryable<LearnersLicence> GetLearnersLicences()
{
return this.ObjectContext.LearnersLicences.Include("LicenceClass").Include("LicenceTypes");
}
Related
I have been tasked with create a tracker for company work flow.
I have 10 tables with data in them. There are attributes all the tables have in common. I made a table with those attributes, giving those records a unique ID that could join them to the unique attribute records of the original tables. I am also linking a personnel table to the original tables. All of these tables exist on my SQL Server back end. I Have made a query in Access that displays all the information I was given. I'm going to use the forms in access as a front end to display, edit, and add records.
The issue I am encountering is that I can not write to a query that has externally linked tables. I have spent a lot of time normalizing this data and I know I can get around it by making tables with redundant attributes in SQL and not writing to the query, but rather write to the linked tables instead. Just wondering if there is a way around this.
Thanks
In general, even without linked tables, such queries are NOT updatable.
The general approach when working with multiple tables is to use sub forms for the child tables. That way, each form is only bound to one table. (You are free even to bind such forms directly to the linked table).
Thus, you might say have a customer table and then a table of invoices. So your main form will display the one customer and is bound to that one table.
In the sub form, you can then display all of the invoices.
So to combine multiple tables into a form or screen that allows users to update the data, or add more data, you don’t build some query that joins all the data together, but simply combine several forms into one form. But each of those separate forms will display data from the given related child table.
Here is a typical invoice form thus built in Access:
The top part is the “main” form of an invoice. It is bound to the customer table – one record. Then the multiple lines of detail is the invoice details table. So the form does NOT use queries, but each part of the form and sub forms are bound to the given related tables. You are binding each form directly to the linked table (or tables if you need to show related data like above).
This approach allows you to cobble together a set of forms that edit related tables, but each form is bound directly to the linked table.
So the fact of linked tables or not is moot – such queries are not used to edit data and such queries from link or non-linked tables are NOT updatable.
So your form + sub forms will follow the pattern of related tables that you need to work together as one whole view and means to edit data. You don’t need nor want to use a query to fill these forms.
You most certainly will provide some kind of “search” form, or some means to pull up say one customer invoice, and that invoice along with its sub forms will display the related data, and also allow editing of that data.
I'm very new to FileMaker currently working on a Mac. I've been assigned a new simple system to work towards completing and I have bumped into some issues with database relationships. I've got experience with PHP/MySQL databases connections etc. but FileMaker seems to require a somewhat different mindset and approach.
I'll try to explain this as simply as I can.
Here's the table relationships in my database
What I'm trying to do is a list of "to-do" notes, an interactive menu where the user can add things that needs to be done. I've done this with a portal on a layout based on the table "site". The portal is based on the table "todo_notes", which is connected to site through the "site_id".
Here's what it looks like in browse mode
What I'm having problems with is adding a relationship between the todo_notes and contacts. The contacts are two separate tables called "county_contacts" and "property_owner_contacts". What I want to accomplish is the possibility for the user to, from a dropdown-list, add a single contact from these two tables. Preferably I'd like to sort of merge these two tables into the same dropdown-list.
Let me know if you need any other information or a better explanation of my issue. Any help is very welcome!
If you have a single contacts table with foreign keys for both county and property owner tables, that would let you have a single list for all contacts. From there you could also build a value list based on a relationship, for example to filter only contacts that belong to either county or property owners.
If you then need to further normalize the tables, fields that pertain to either relationship exclusively could be moved to another table from there, as a one to one relationship, if that is a concern.
The Short Answer
You need to create a Contacts table. Filemaker has no way of dynamically generating value lists. Instead, you can base a value list on any field, therefore, the only way of generating a list of the contact names would be if they were all in the same table.
The Long Answer
Because Filemaker only allows us to use ONE field for a value list, we must create a new table for the contact. I would recommend that you replace the two contact tables with a single contact table,(seeing as the fields look the same between the two tables) and then add a toggle on the contact for Owner or County. However, you could also create a single contact table for all of the fields that overlap that has foreign keys to the owner and county tables.
You would then use the fullname field from the contact and be good to go.
That is, assuming that you did not want to filter the contacts at all or only show contacts associated with this site.
To start with, I highly recommend using the Anchor-buoy method for organizing the relationship graph. Here's an explanation of the anchor-buoy method: http://sixfriedrice.com/wp/six-fried-rice-methodology-part-2-anchor-buoy-and-data-structures/ . It's just a convention, but will help you with the idea of context in FileMaker. It's widely accepted among the FileMaker community as the "right" way to organize a relationship graph. I will continue my explanation using this method.
Each Table Occurrence (the boxes in the graphs, or TO) represents a unique context from which you can view and edit information. In the anchor buoy method, each Table only has one "anchor" TO. I would recommend only using anchor TO's for the context of your layouts. Then, your portal, and any other corresponding information, will be on your buoy TO's. Here is what your new portal relationship would look like. You would select fields from your buoy TO's to use in the portal.
The easiest way to filter your value list by only contacts associated with this site would be to create a foreign key from the contact table to the site, and then add a TO to the graph, for the contact table. You would then click "Include only related values starting from" radio button, and specify your new TO.
I have a system whereby you can create documents. You select the document type to create and a form is displayed. Data is then added to the form, and the document can be generated. In Laravel things are done via Models. I am creating a new Model for each document but I don't think this is the best way. An example of my database :
So at the heart of it are projects. I create a new project; I can now create documents for this project. When I select project brief from a select box, a form is displayed whereby I can input :
Project roles
Project Data
Deliverables
Budget
It's three text fields and a standard input field. If I select reporting doc from the select menu, I have to input the data for this document (which is a couple of normal inputs, a couple of text fields, and a date). Although they are both documents, they expect different data (which is why I have created a Model for each document).
The problems: As seen in the diagram, I want to allow supporting documents to be uploaded alongside a document which is generated. I have a doc_upload table for this. So a document can have one or more doc_uploads.
Going back to the MVC structure, in my DocUpload model I can't say that DocUpload belongs to both ProjectBriefDoc and ProjectReportingDoc because it can only belong to one Model. So not only am I going to create a new model for every single document, I will have to create a new Upload model for each document as well. As more documents are added, I can see this becoming a nightmare to manage.
I am after a more generic Model which can handle different types of documents. My question relates to the different types of data I need to capture for each document, and how I can fit this into my design.
I have a design that can work, but I think it is a bad idea. I am looking for advice to improve this design, taking into account that each document requires different input, and each document will need to allow for file uploads.
You don't need to have a table/Model for each document type you'll create.
A more flexible approach would be to have a project_documents table, where you'll have a project_id and some data related to it, and then a doc_uploads related to the project_documents table.
This way a project can have as many documents your business will ever need and each document can have as many files as it needs.
You could try something like that:
If you still want to keep both tables, your doc_upload table in your example can have two foreign keys and two belongsTo() Laravel Model declarations without conflicts (it's not a marriage, it's an open relationship).
Or you could use Polymorphic Relations to do the same thing, but it's an anti-pattern of Database Design (because it'll not ensure data integrity on the database level).
For a good reference about Database Design, google for "Bill Karwin" and "SQL Antipatterns".
This guy has a very good Slideshare presentation and a book written about this topic - he used to be an active SO user as well.
ok.
I have a suggestion..you don't have to have such a tight coupling on the doc_upload references. You can treat this actually as a stand alone table in your model that is not pegged to a single entity.. You can still use the ORM to CRUD your way through and manage this table..
What I would do is keep the doc_upload table and use it for all up_load references for all documents no matter what table model the document resides in and have the following fields in the doc_upload table
documenttype (which can be the object name the target document object)
documentid_fk (this is now the generic key to a single row in the appropriate document type table(s)
So given a document in a given table.. (you can derive the documenttype based on the model object) and you know the id of the document itself because you just pulled it from the db context.. should be able to pull all related documents in the doc_upload table that match those two values.
You may be able to use reflection in your model to know what Entity (doc type ) you are in.. and the key is just the key.. so you should be able.
You will still have to create a new model Entity for each flavor of project document you wish to have.. but that may not be too difficult if the rate of change is small..
You should be able to write a minimum amount of code to e pull all related uploaded documents into your app..
You may use inheritance by zero-or-one relation in data model design.
IMO having an abstract entity(table) called project-document containing shared properties of all documents, will serve you.
project-brief and project-report and other types of documents will be children of project-document table, having a zero-or-one relation. primary key of project-document will be foreign key and primary key of the children.
Now having one-to-many relation between project-document and doc-upload will solve the problem.
I also suggest adding a unique constraint {project_id, doc_type} inside project-document for cardinal check (if necessary)
As other answers are sort of alluding to, you probably don't want to have a different Model for different documents, but rather a single Model for "document" with different views on it for your different processes. Laravel seems to have a good "templating" system for implementing views:
http://laravel.com/docs/5.1/blade
http://daylerees.com/codebright-blade/
I have a project that is using EF6 Database first mapped to a SQL database. This is all new so I control the EF model as well as the database schema.
I currently have a table that I'll call Vehicle for simplicity. I use a discriminator column to get subclass Entities Car and Truck. This all works fine.
Now I need to do a 'soft delete' and move any deleted vehicles to a VehicleHistory table. (After trying this w/ EF i will probably use a SQL transaction). This needs to be reviewable so I need this history table mapped as well, but I would like to keep it within the inheritance hierarchy so its easily reused in other classes.
My idea was to create 'vehiclecurrent' and 'vehiclehistory' tables with FK's to Vehicle for shared columns. i would then use TPT in EF to get 'carcurrent','carhistory', ect... derived from my TPH classes(so e.g. carhistory->car->vehicle). This is not working and I get Error 3034: "Entities w/ different keys are mapped to the same row"
So my question is basically how can I pull this off? Will this approach work and how, or is there another way to accomplish this? Thanks!
It came up again today how to handle allowing users to add custom fields to the standard entity schemas delivered in your product's database. I favour actually providing a function that gives the user limited DDL functions, so they can actually add a new, custom field to a table. Another approach is to have a separate table for custom fields, e.g. Customers, and CustomersEx, where only CustomersEx can change, but here updates become trickier than normal. The last and most badass option that we discussed was providing a EAV table, where rows are entity name, field name, field value.
Which approach is best?
EAV that is added to the existing relational structure. There is a whitepaer published by SQL Server CAT (Customer Advisor Team) on this topic. Although is vendor specific, the principels discussed and the solutions proposed apply to most RDBMS: Best Practices for Semantic Data Modeling for Performance and Scalability
I favor your second idea. We do something similar but call the tables Attr[ibute] tables, e.g. Company, CompanyAttr. The attributes are a collection in our business object (1:M) and NHibernate handles database operations. We explicitly display these fields as attributes in the UI and don't try to display them as if they were additional fields in the table.
I favor adding fields to a table via DDL, but that table should be separate from the main table. That way, you can script changes to your database schema without affecting your users' custom field additions. A right-join is easy enough to accomplish, and you won't need the record in the separate table if there are no custom fields.
If you just want to display data in a vertical fashion, EAV tables can be a good choice. You can also run a pivot query to display them horizontally.