I'm just starting to use Entity Framework Designer. I would like to ask how should I create my Entity files. I would like to have like 10 tables and all of them will be linked to at least one other table by some row. Should I create just one file and put all my models there or create a separate file for each model.
I don't know if this is even a question but I could find my answer on Google. I didn't know how to define it actually... :D
So if you have any tips on how I should model my database that will be awesome. Also if you have any more information on when I should use different Entity files that will be useful too.
I have used MySQL designer in the past but in there as far as i can remember you just move the model into the designer and you can make relations. So I'm kinda keen into doing that (all models in one Entity File) but wanted to check with you first guys.
just try this plugin for VS http://visualstudiogallery.msdn.microsoft.com/72a60b14-1581-4b9b-89f2-846072eff19d to generate your classes from existing db
I'm interested in displaying 1-5 model instances using forms on a page using a grid similar to something one would find in a desktop database application. I understand I would need to use multiple forms or formsets but an additional requirement is that I'd prefer it to be in more of a grid format with each model's fields being display in columns with common field labels on the y-axis.
I should have the ability to edit multiple columns (so in effect, model instances) at the same time and then commit either the single column (model instance) or commit all. I'd also like to be able to highlight the changed cells that have changed to give visual feedback to the user that there are pending changes.
Sorry for the rather long list of requirements and I'm aware this probably requires a few different technologies/techniques to achieve. I'm throwing this out there because I'm asking this kind community for guidance on what components/technologies I should look at. If luck would have it, there would be some jQuery component that can handle this for me almost out of the box. If not, some guidance on achieving the editing of multiple model instances would be of help.
I will also need to build in versioning in case the data displayed on the view page is stale and to prevent overwriting a newer commit. I'd probably achieve the latter using a versioning field in the table that will perform the check and handle it accordingly.
Also, Flask and Django are both options for the engine and WTForms look to be promising at least at first look.
Thanks
There is no such ready to use solution in Django. Just create your custom form that handles as many instances as you want and do anything that you want, or extend formset.
Scaffolding works like magic. However, there are fields in my table that does necessarily needed to be edited. How can I customize $scaffold so that I won't manually create the view for editing my table. Thanks guys.
From the CakePHP manual on scaffolding:
[Scaffolding is] a loose structure you throw up real quick during the beginning of a project in order to get started. It isn’t meant to be completely flexible, it’s meant as a temporary way to get up and going. If you find yourself really wanting to customize your logic and your views, it’s time to pull your scaffolding down in order to write some code.
What you can do is use cake bake on the command line to create basic views, and then you can modify them to your specific needs.
Migrations are undoubtedly better than just firing up phpMyAdmin and changing the schema willy-nilly (as I did during my php days), but after using them for awhile, I think they're fatally flawed.
Version control is a solved problem. The main function of migrations is to keep a history of changes to your database. But storing a different file for each change is a clumsy way to track them. You don't create a new version of post.rb (or a file representing the delta) when you want to add a new virtual attribute -- why should you create a new migration when you want to add a new non-virtual attribute?
Put another way, just as you check post.rb into version control, why not check schema.rb into version control and make the changes to the file directly?
This is functionally the same as keeping a file for each delta, but it's much easier to work with. My mental model is "I want table X to have such and such columns (or really, I want model X to have such and such properties)" -- why should you have to infer from this how to get there from the existing schema; just open up schema.rb and give table X the right columns!
But even the idea that classes wrap tables is an implementation detail! Why can't I just open up post.rb and say:
Class Post
t.string :title
t.text :body
end
If you went with a model like this, you'd have to make a decision about what to do with existing data. But even then, migrations are overkill -- when you migrate data, you're going to lose fidelity when you use a migration's down method.
Anyway, my question is, even if you can't think of a better way, aren't migrations kind of gross?
why not check schema.rb into version control and make the changes to the file directly?
Because the database itself is not in sync with version control.
For instance, you could be using the head of the source tree. But you're connecting to a database that was defined as some past version, not the version you have checked out. The migrations allow you to upgrade or downgrade the database schema from any version and to any version, incrementally.
But to answer your last question, yes, migrations are kind of gross. They implement a redundant revision control system on top of another revision control system. However, neither of these revision control systems is really in sync with the database.
Just to paraphrase what others have said: migrations allow you to protect the data as your schema evolves. The notion of maintaining a single schema.rb file is attractive only until your app goes into production. Thereafter, you'll need a way to migrate your existing users' data as your schema changes.
There are also data-related issues that are important to consider, which migrations solve.
Say an old version of my schema has a feet and inches column. For efficiency purposes, I want to combine that into just an inches column to make sorting and searching easier.
My migration can combine all of the feet and inches data into the inches column (feet * 12 + inches) while it's updating the database (i.e. just before it removes the feet column)
Obviously this being in a migration makes it automatically work when you later apply the changes to your production database.
As it stands, they're annoying and inadequate but quite possibly the best option we have available to us at present. Quite a few smart people have spent quite a lot of time working on the problem and this, so far, is about the best they've been able to come up with. After about 20 years of mostly hand-coding database version updates, I came very rapidly to appreciate migrations as a major improvement when I found ActiveRecord.
As you say, version control is a solved problem. Up to a point I'd agree: it's very solved for text files in particular, less so for other file types and not really very much at all for resources such as databases.
How do migrations look if you view them as version control deltas for databases? They're the sum of the deltas you have to apply to get a schema from one version to another. I'm not aware that even git, for all its super-powerfulness, can take two schema files and generate the necessary DDL to do that.
As far as declaring table content in the model, I believe that's what DataMapper does (no personal experience). I think there may be some DDL inference capabilities there as well.
"even if you can't think of a better way, aren't migrations kind of gross?"
Yes. But they're less gross than anything else we have. Do please let us know when you've completed the non-gross alternative.
I suppose given "even if you can't think of a better way", then yes, in the grand scheme of things, migrations are kind of gross. So are Ruby, Rails, ORMs, SQL, web apps, ...
Migrations have the (not insignificant) advantage that they exist. Gross-but-exists tends to win out over Pleasant-but-nonexistent. I'm sure there probably are pleasant and nonexistent ways to migrate your data, but I'm not sure what that means. :-)
OK, I'm going to take a wild guess here and say that you're probably working all by yourself. In a group development project the power of each individual to take responsibility for just his/her changes to the database required for the code that developer is writing is much much more important.
The alternative is that larger groups of programmers (e.g. 10-15 Java developers where I work) end up relying on a couple of dedicated full time database administrators to do that along with their other maintenance, optimization, etc. duties.
I understand the reason behind not auto refreshing your .dbml (Linq2Sql), .edmx (Linq2Entities) or .hbm.xml (NHibernate). In each of these ORM solutions you need to update these files if you have changes in the database. Is there a way to refresh these files automatically if you are 100% sure that it wont break anything?
I am reasonably familiar with Migrations in RoR. Is there a dependabale Migration tool in the .NET world ?
In general, how do you stay agile with database design and dont recreate these mapping files manually again and again?
Please provide a link if this question is a duplicate. I was not able to find one.
I'm not sure what your hesitation about updating the EDMX is. Just go ahead and update your model from the database. Chances are very good it will work. But if it doesn't, just get the old version from source control, and make the changes manually.
With LINQ to SQL, on the other hand, it's harder, because there is no update feature. You have to remove the changed objects from your model, re-add them, and re-apply any changes you have made, manually. Again, source control is vital here; you'll want to diff the XML files from the previous version to make sure you didn't forget anything.
I'm not sure what your question about migrations means. Yes, there is a tool (RikMigrations), which does a similar thing as migrations in Rails. But migrations, of course, change your database metadata. They don't change your ORM mapping. That's done elsewhere, both in Rails and in .NET.