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This article mainly introduces "how to effectively carry out ADO.NET Entity Framework query". In daily operation, I believe many people have doubts about how to effectively carry out ADO.NET Entity Framework query. The editor consulted all kinds of data and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about "how to effectively carry out ADO.NET Entity Framework query"! Next, please follow the editor to study!

In the database application, the transaction mode is often used to ensure that the data is correctly loaded into the database, and Rollback backtracking is performed in the event of an error. In Entity Framework, the transaction procedure is performed through the TransactionScope in the System.Transactions naming space.

For developers who are very familiar with operating the database, it is common to retrieve data from the database. There are too many things that can be done by Transact-SQL 's SELECT statement, including relational links, subqueries and Recursive Query, and so on.

Of course, the query ability in ADO.NET Entity Framework should not be too weak, but Entity SQL is only a subset of Transact-SQL and cannot achieve all the functions of Transact-SQL. For this reason, when designing data, you should package possible subscription queries using check tables, stored procedures, or user functions (UDFs). Developers can use simple queries when running programs, which is the job of DBA.

Entity SQL can achieve a large number of SELECT capabilities of Transact-SQL, but there will be some limitations. Some of the common limitations listed are as follows:

The query form and location must have an alias (Alias):

In the past, in Transact-SQL, you did not need an alias to access the database, but in Entity SQL, you must use an alias to reference before you can access Entity, for example:

SELECT a FROM T (Transact-SQL) SELECT n.a FROM T AS a (Entity SQL) SELECT T.a FROM T (Entity SQL with implicit alias)

If you do not want to specify an alias, specify that the name of the table ADO.NET Entity Framework will do an internal alias conversion. To extract all bits in Transact-SQL, we will use * to indicate, but this is not supported in Entity SQL. You must clearly indicate the name of the bit to be extracted, for example:

Transact-SQL: select b + c, count (*), sum (a) from T group by b + c Entity SQL: select k, count (t.a), sum (t.a) from T AS t group by b + c AS k so far, the study on "how to effectively perform ADO.NET Entity Framework query" is over, hoping to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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