The .NET Entity framework is giving me the following error:
"The table/view 'Foo.dbo.vwFoo' does not have a primary key defined and no valid primary key could be inferred. This table/view has been excluded. To use the entity you will need to review your schema, add the correct keys and uncomment it."
The view is a collection of a variety of tables and calculations. What I'd like to do is create a "logical key" using one of the columns that I know should be unique. I can't figure out how to do this in SQL Server Manager 2005 (not a DBA.)
Anyone know how I could accomplish this?
The EF can't find the PK, because VIEWs don't have PKs. However, if the view returns a unique column, you can tell the EF that this is the "PK."
It's explained in this tip: How to work with Updatable Views
Related
I'm relatively new to Entity Framework.
I created a database with two tables: Accounts and Assignments.
Accounts has an AccountId primary key which is used as a foreign key in the Properties table. I really like that the Entity Framework automatically picks up the foreign key relationship and allows me to access rows in Assignments as a property of each row from Accounts.
I went ahead and created a new View object that returns all the columns from Accounts along with some other information. However, when I get the data from the View in SQL using the Entity Framework, it is no longer automagically referencing the associated rows in the Assignments table.
How can I get the desired behavior using Views with Entity Framework
This can work in EF, but the EF designer can't infer your FK out of the view, since the DB doesn't tell it where the FKs on view columns are (since they're naturally on the underlying tables, not the view itself).
You'll need to manually edit your EDMX, either via the designer or in XML, to get these properties.
The solution that worked for me was to include the appropriate data in the view so I didn't need to use the FK.
For example, include the PK's for the Assignment table in the view by adding the appropriate SQL to the view.
That way I could join to the view in LINQ without needing to refer to a generated property in the EDMX.
I am using Fluent NHibernate (which I am fairly new to) in an application I am developing using a legacy Oracle DB. The DB has composite keys which are comprised of foreign keys and database generated columns. The generated columns are supplied by calling a DB function with the table name, and one of the other foreign key parts. The generated composite key parts are not unique, and I cannot change this. The generated key parts are often used as foreign keys on other tables too.
If I create entity mapping which specifies the composite key as it is in the database, then we cannot use any identity generation strategies, which breaks unit of work
If I create entity mapping which specifies only the generated column as the primary key, then I can use trigger-identity to generate the ids, and I get unit of work, but I then have a problem when I want to update, or access a child collection: The other parts of the key are not included in the WHERE statement.
Can anyone give me any advice on how to proceed?
If I stick with mapping composite keys, can I extend nhibernate to output the SQL to use trigger-identity? If so, can you suggest a starting point?
If I map a single column key, can I include other properties in a WHERE clause for HasMany mapping and Updates?
Unfortunately, as you have already found out, there is no support at all for this setup.
My suggestion is to do INSERTS manually (using custom SQL, for example). And yes, this breaks the UoW, but that is true of identity too.
I got this error:
"The table/view 'database.dbo.table' does not have a primary key defined and no
valid primary key could be inferred. This table/view has been excluded. To use
the entity, you will need to review your schema, add the correct keys, and
uncomment it."
So, I un-commented it, added EntityKeys, EntityTypes, and a query. Everything worked fine, until I "Update Model From Database", which erased all my changes.
How can you get Entity Framework to recognize the view under the "Update Model From Database"? Is there anything you can add to the Microsoft SQL 2005 view so that EF could pickup as the primary key fields?
My view only has two fields:
ID int not null, -- PK
SKU int null
This is a known EF Designer limitation. The Store part of the model is regenerated by the Update Model From Database wizard, this is the reason of the problem.
This problem was already discussed at the Devart Entity Framework Support forum here.
Is it beneficial to use multicolumn (composite) primary keys for a many to many relationship table when using Linq to SQL?
Or should I just add an identity column as a non-clustered primary key and index the FK columns appropriately?
Not a LINQ issue. If you need them for your schema, then use them. If you don't, don't. Either way, LINQ will handle your schema just fine.
One area that LINQ to SQL doesn't handle well are multy column / key mapping table that are used to connect a many to many relationship but I wouldn't say this strickly falls under the category that your question addresses. You can still perform CRUD operations on a mapping table within LINQ but LINQ cannot walk the relationship presented by a many to many mapping table. (LINQ works fine with one to one and one to many tables.)
I can't speak to any issue with the Entity Framework but again, I would be very surprised if the EF had any issues with multi-column / multi-key tables.
If it makes sense in your domain to have a multi-column composite key, then use one. Otherwise use the usual identity column as the surrogate primary key.
EDIT: that was general advice and not taking into account any technical aspects of implementing using LINQtoSQL. These may be of interest:
How to: Handle Composite Keys in Queries (LINQ to SQL)
LINQ To SQL Samples
Linq to SQL DTOs and composite objects
I need to use tables from a DB which I cannot alter (using linked server).
So part of my schema is a view on these table and I cannot create an FK in my DB.
When I come to creating the association in ADO.NET Entity Framework I am getting problems because a second column on the table from the external DB has an index on it and the EF is creating an Entity Key for it (it's the name descr of the record - I think they just wanted to speed the ordering on it).
When I take the Entity Key off this column in the EF entity it complains that I need it because the underlying table has a key on it.
If I leave it in I cannot map it onto anything in the table mapping of EF.
Does anyone know what I should do please?
You will have to edit the XML and remove the column from the key. Find the <EntityType> tag in the <edmx:StorageModels> section (SSDL content). Delete any <PropertyRef> in the <Key> that is not actually part of the primary key.
Once you do this, you can set "Entity Key" on the corresponding scalar property in the designer to false, and EF won't get mad. You will also not be asked to map this column in associations anymore.