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This is useful independently of whether new EDM constructs are used in the resulting model.
An obvious question at this point would be why not just use traditional database views for this.
In order to provide a mechanism for storing data modeled using the EDM in relational databases, the ADO.
NET Entity Framework houses a powerful client-views infrastructure designed to manage the transformations between the logical database schema that's present in the relational store and the conceptual EDM schema used by the application.
Indeed, there are many scenarios where the right framework can empower an application developer to focus on the needs of the application as opposed to the complexities of bridging disparate data representations. NET is to raise the level of abstraction for data programming, thus helping to eliminate the impedance mismatch between data models and between languages that application developers would otherwise have to deal with. NET will LINQ-enable many data access components: LINQ to SQL, LINQ to Data Set and LINQ to Entities. NET Entity Framework, what problem spaces it is targeting and how its various components address those problems.
NET Framework Language-Integrated Query Summary: Eliminate the impedance mismatch between data models and between languages that application developers would otherwise have to deal with new features available in the upcoming version of ADO. NET Entity Framework: Object Services LINQ to Entities: Language-Integrated Query References Appendix When one takes a look at the amount of code that the average application developer must write to address the impedance mismatch across various data representations (for example objects and relational stores) it is clear that there is an opportunity for improvement.
NET Entity Framework: Modeling at the Rght Level of Abstraction ADO.
Since currently most applications are written on top of relational databases, sooner or later they'll have to deal with the data represented in a relational form. Total Due In addition to the issues pointed out above, both queries present another interesting problem: they return information about employees and sales persons respectively.
Let's say that another application, this time the sales system, is also built on top of the same database. Furthermore, since the results are simply projections, the source information that describes where the data came from is lost, requiring developers to explicitly tell the system how inserts, updates and deletes should be done by using specific SQL statements.
Using the same logical schema we used in the previous example, we would have to use the following query to obtain all of the sales persons that have sales orders for more than 0,000: SELECT Sales Person ID, First Name, Last Name, Hire Date FROM Sales Person sp INNER JOIN Employee e ON sp. The issues we just discussed fall into two main classes: , which consists of a data model and a set of design-time and run-time services that allow developers to describe the application data and interact with it at a "conceptual" level of abstraction that is appropriate for business applications, and that helps isolate the application from the underlying logical database schemas.
Even if there was a higher-level conceptual model used during the design, that model is typically not directly "executable", so it needs to be translated into a relational form and applied to a logical database schema and to the application code. However, you cannot ask the system for an "employee" or a "sales person".
While the relational model has been extremely effective in the last few decades, it's a model that targets a level of abstraction that is often not appropriate for modeling most business applications created using modern development environments. Here is a fragment of a variation of the Adventure Works sample database that's included in Microsoft SQL Server 2005: Figure 1 If we were building a human-resources application on top of this database and at some point wanted to find all of the full-time employees that were hired during 2006 and list their names and titles, we'd have to write the following SQL query: The problems highlighted above are related to the fact that the logical database schema is not always the right view of the data for a given application. The system does not have knowledge of what that means.
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