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What is Data adapter?
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Posted Date :
October 19, 2010
Data adapter are objects that connect one or more command objects to a dataset object. They provide logic that gets the data from the data store and populates the tables in the dataset, or pushes the changes in the dataset back into the data store.
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What is Data adapter?
What is the use of data adapter?
These objects connect one or more Command objects to a Dataset object. They provide logic that would get data from the data store and populates the tables in the Dataset, or pushes the changes in the Dataset back into the data store.
. An OleDbDataAdapter object is used with an OLE-DB provider
. A SqlDataAdapter object uses Tabular Data Services with MS SQL Server.
What are basic methods of Data adapter?
Fill :- Executes the SelectCommand to fill the DataSet object with data from the data source. It an also be used to update (refresh) an existing table in a DataSet with changes made to the data in the original datasource if there is a primary key in the table in the DataSet.
FillSchema :- Uses the SelectCommand to extract just the schema for a table from the data source, and creates an empty table in the DataSet object with all the corresponding constraints.
Update:- Calls the respective InsertCommand, UpdateCommand, or DeleteCommand for each inserted, updated,or deleted row in the DataSet so as to update the original data source with the changes made to the content of the DataSet. This is a little like the UpdateBatch method provided by the ADO Recordset object, but in the DataSet it can be used to update more than one table.
When do you need to specify an external data source by using a linked server?
When you need to access a different instance.
What is Method used to bind the data into gridview ?
DataBind() Method used to bind the data into gridview
What is the .NET that allows the retrieval of data by a unique key?
HashTable is the .NET collection class that allows the retrieval of data by a unique key
What is managed code and managed data?
Managed code is code that is written to target the services of the Common Language Runtime (see What is the Common Language Runtime?). In order to target these services, the code must provide a minimum level of information (metadata) to the runtime. All C#, Visual Basic.NET, and _JScript.NET code is managed by default. Visual Studio.NET C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/CLR).
Closely related to managed code is managed data-data that is allocated and de-allocated by the Common Language Runtime's garbage collector. C#, Visual Basic, and _JScript.NET data is managed by default. C# data can, however, be marked as unmanaged through the use of special keywords. Visual Studio.NET C++ data is unmanaged by default (even when using the /CLR switch), but when using Managed Extensions for C++, a class can be marked as managed by using the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector. In addition, the class becomes a full participating member of the .NET Framework community, with the benefits and restrictions that brings. An example of a benefit is proper interoperability with classes written in other languages (for example, a managed C++ class can inherit from a Visual Basic class). An example of a restriction is that a managed class can only inherit from one base class.
What is data structure?
A data structure is a way of organizing data that considers not only the items stored, but also their relationship to each other. Advance knowledge about the relationship between data items allows designing of efficient algorithms for the manipulation of data.
List out the areas in which data structures are applied extensively?
3.Database Management System,
4.Statistical analysis package,
What are the major data structures used in RDBMS, Network data model & Hierarchical data model.
RDBMS - Array (i.e. Array of structures)
Network data model - Graph
Hierarchical data model - Trees
What is the data structures used to perform recursion?
Stack. Because of its LIFO (Last In First Out) property it remembers its 'caller' so knows whom to return when the function has to return. Recursion makes use of system stack for storing the return addresses of the function calls.
Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written, explicit stack is to be used.
What operator tests column for the absence of data?
IS NULL operator
Describe the three levels of data abstraction?
The are three levels of abstraction:
1.Physical level: The lowest level of abstraction describes how data are stored.
2.Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
3.View level: The highest level of abstraction describes only part of entire database.
How is the data structure of System R different from the relational structure?
Unlike Relational systems in System R
1.Domains are not supported
2.Enforcement of candidate key uniqueness is optional
3.Enforcement of entity integrity is optional
4.Referential integrity is not enforced
What is Data Independence?
Data independence means that "the application is independent of the storage structure and access strategy of data". In other words, The ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
Two types of Data Independence:
1.Physical Data Independence: Modification in physical level should not affect the logical level.
2.Logical Data Independence: Modification in logical level should affect the view level.
NOTE: Logical Data Independence is more difficult to achieve
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