Aug 05, 2007 LINQ to SQL uses optimistic concurrency be default. LINQ to SQL is pure in memory operation, because you normally get the data from database and store them. Also as per the link if i write all the delete queries and the save query in one transaction scope. And error occurs in any one line. All the query above that. Atomicity requires that each transaction is 'all or nothing': if one part of the transaction fails, the entire transaction fails, and the database state is left.

About the Author Bart McDonough is the Principal Consultant at Incline Technical Group, a Microsoft consulting firm specializing in custom software development and training. He's been developing software for over ten years and works across the whole Microsoft technology stack, specializing in SharePoint, Silverlight and ASP.NET MVC solutions. He attends and speaks at.NET and SharePoint User Groups and was active in beta testing Silverlight 3 and RIA Services. He spends his free time with his wife and three kids and takes full advantage of the hiking, skiing, and world-class brewpubs available to him in Colorado. He can be contacted via and.

• SQL-86 • SQL-89 • • • • • • • Influenced by Influenced,,,,,, • at Wikibooks SQL ( ( ) S-Q-L, 'sequel'; Structured Query Language) is a used in programming and designed for managing data held in a (RDBMS), or for stream processing in a (RDSMS). In comparison to older read/write like or, SQL offers two main advantages: first, it introduced the concept of accessing many records with one single command; and second, it eliminates the need to specify how to reach a record, e.g. With or without an index. Originally based upon and, SQL consists of many types of statements, which may be informally classed as, commonly: a (DQL), a (DDL), a (DCL), and a (DML). The scope of SQL includes data query, data manipulation (insert, update and delete), data definition ( creation and modification), and data access control. Although SQL is often described as, and to a great extent is, a (), it also includes elements. SQL was one of the first commercial languages for 's, as described in his influential 1970 paper, 'A Relational Model of Data for Large Shared Data Banks'.

Despite not entirely adhering to, it became the most widely used database language. SQL became a of the (ANSI) in 1986, and of the (ISO) in 1987. Since then, the standard has been revised to include a larger set of features. Despite the existence of such standards, most SQL code is not completely portable among different database systems without adjustments. Contents • • • • • • • • • • • History [ ] SQL was initially developed at by and in the early 1970s. This version, initially called SEQUEL ( Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasi-relational database management system,, which a group at had developed during the 1970s.

The acronym SEQUEL was later changed to SQL because 'SEQUEL' was a of the aircraft company. In the late 1970s, Relational Software, Inc. (now ) saw the potential of the concepts described by Codd, Chamberlin, and Boyce, and developed their own SQL-based with aspirations of selling it to the,, and other agencies. In June 1979, Relational Software, Inc. Introduced the first commercially available implementation of SQL, V2 (Version2) for computers.

After testing SQL at customer test sites to determine the usefulness and practicality of the system, IBM began developing commercial products based on their System R prototype including,, and, which were commercially available in 1979, 1981, and 1983, respectively. Design [ ] SQL deviates in several ways from its theoretical foundation, the and its. In that model, a table is a of tuples, while in SQL, tables and query results are of rows: the same row may occur multiple times, and the order of rows can be employed in queries (e.g. In the LIMIT clause).

Critics argue that SQL should be replaced with a language that strictly returns to the original foundation: for example, see. Find more about SQLat Wikipedia's • from Wiktionary • from Wikimedia Commons • from Wikibooks • from Wikiversity •: transcript of a reunion meeting devoted to the personal history of relational databases and SQL.

• Collection documents the H2 committee's development of the NDL and SQL standards. • In this oral history Chamberlin recounts his early life, his education at and, and his work on relational database technology. How I Met Your Mother Season 8 Torrent Pirate Bay. Chamberlin was a member of the System R research team and, with, developed the SQL database language. Chamberlin also briefly discusses his more recent research on XML query languages. • This comparison of various SQL implementations is intended to serve as a guide to those interested in porting SQL code between various RDBMS products, and includes comparisons between SQL:2008, PostgreSQL, DB2, MS SQL Server, MySQL, Oracle, and Informix. • - An introduction to real-time processing of streaming data with continuous SQL queries •.

Last month I started a blog post series covering LINQ to SQL. LINQ to SQL is a built-in O/RM (object relational mapping) framework that ships in the.NET Framework 3.5 release, and which enables you to easily model relational databases using.NET classes. You can then use LINQ expressions to query the database with them, as well as update/insert/delete data from it. Below are the first two parts of my LINQ to SQL series: • • In today's blog post I'll be going into more detail on how to use the data model we created in the post, and show how to use it to query data within an ASP.NET project. Northwind Database Modeled using LINQ to SQL In of this series I walked through how to create a LINQ to SQL class model using the LINQ to SQL designer that is built-into VS 2008. Below is the class model that we created for the Northwind sample database: Retrieving Products Once we have defined our data model classes above, we can easily query and retrieve data from our database.

LINQ to SQL enables you to do this by writing LINQ syntax queries against the NorthwindDataContext class that we created using the LINQ to SQL designer above. For example, to retrieve and iterate over a sequence of Product objects I could write code like below: In the query above I have used a 'where' clause in my LINQ syntax query to only return those products within a specific category. I am using the CategoryID of the Product to perform the filter.

One of the nice things above LINQ to SQL is that I have a lot of flexibility in how I query my data, and I can take advantage of the associations I've setup when modeling my LINQ to SQL data classes to perform richer and more natural queries against the database. For example, I could modify the query to filter by the product's CategoryName instead of its CategoryID by writing my LINQ query like so: Notice above how I'm using the 'Category' property that is on each of the Product objects to filter by the CategoryName of the Category that the Product belongs to. This property was automatically created for us by LINQ to SQL because we modeled the Category and Product classes as having a many to one relationship with each other in the database.

For another simple example of using our data model's association relationships within queries, we could write the below LINQ query to retrieve only those products that have had 5 or more orders placed for them: Notice above how we are using the 'OrderDetails' collection that LINQ to SQL has created for us on each Product class (because of the 1 to many relationship we modeled in the LINQ to SQL designer). Visualizing LINQ to SQL Queries in the Debugger Object relational mappers like LINQ to SQL handle automatically creating and executing the appropriate SQL code for you when you perform a query or update against their object model. One of the biggest concerns/fears that developers new to ORMs have is 'but what SQL code is it actually executing?' One of the really nice things about LINQ to SQL is that it makes it super easy to see exactly what SQL code it is executing when you run your application within the debugger. Starting with Beta2 of Visual Studio 2008 you can use a new LINQ to SQL visualizer plug-in to easily see (and test out) any LINQ to SQL query expression. Simply set a breakpoint and then hover over a LINQ to SQL query and click the magnify glass to pull up its expression visualizer within the debugger: This will then bring up a dialog that shows you the exact SQL that LINQ to SQL will use when executing the query to retrieve the Product objects: If you press the 'Execute' button within this dialog it will allow you to evaluate the SQL directly within the debugger and see the exact data results returned from the database: This obviously makes it super easy to see precisely what SQL query logic LINQ to SQL is doing for you. Note that you can optionally override the raw SQL that LINQ to SQL executes in cases where you want to change it - although in 98% of scenarios I think you'll find that the SQL code that LINQ to SQL executes is really, really good.

Databinding LINQ to SQL Queries to ASP.NET Controls LINQ queries return results that implement the IEnumerable interface - which is also an interface that ASP.NET server controls support to databind object. What this means is that you can databind the results of any LINQ, LINQ to SQL, or LINQ to XML query to any ASP.NET control. For example, we could declare an control in a.aspx page like so: I could then databind the result of the LINQ to SQL query we wrote before to the GridView like so: This will then generate a page that looks like below: Shaping our Query Results Right now when we are evaluating our product query, we are retrieving by default all of the column data needed to populate the Product entity classes.

For example, this query to retrieve products: Results in all of this data being returned: Often we only want to return a subset of the data about each product. We can use the new that LINQ and the new C# and VB compilers support to indicate that we only want a subset of the data by modifying our LINQ to SQL query like so: This will result in only this data subset being returned from our database (as seen via our debug visualizer): What is cool about LINQ to SQL is that I can take full advantage of my data model class associations when shaping my data. This enables me to express really useful (and very efficient) data queries. For example, the below query retrieves the ID and Name from the Product entity, the total number of orders that have been made for the Product, and then sums up the total revenue value of each of the Product's orders: The expression to the right of the 'Revenue' property above is an example of using the 'Sum' provided by LINQ. It takes a that returns the value of each product order item as an argument.