Tuesday 6 August 2013

ADO.NET Basic interview questions and ansewers

1.    What are the major difference between classic ADO and ADO.NET?
·          In ADO we have record set and in ADO.NET we have Dataset.
·          In recordset we can only have one table. If we want to accommodate more than one tables we need to do inner join and fill the recordset.
·          Dataset can have multiple tables.
·          All data persist in XML as compared to classic ADO where data persisted in Binary format also.
2.    What two classes are used to read data only?
                 Use the SqlDataReader and OleDbDataReader classes to read data in a forward direction only.
3.    What are the two fundamental objects in ADO.NET?
                 There are the two fundamental objects in ADO.NET are :
·          Data reader
·          Data set
4.    What method is used by the Command classes to execute SQL statements that return single values?
                The Execute scalar method executes SQL commands that return single values.
5.    Which namespaces are used for data access?
·          System.Data
·          System.Data.OleDB
·          System.Data.SQLClient
6.    What is the difference between Dataset and Data reader?
·          Data Reader provides forward only and read only access to data, while the Data set objects can hold more than one table from the same data source as well as the relationships between them.
·          Dataset is a disconnected architecture while data reader is connected architecture.
·          Dataset can persist contents while data reader cannot persist contents they are forward only.
7.    What two types of data providers does ADO.NET supply? What determines which one you should use?
                ADO.NET contains the SQL data provider and the OLE DB data provider. Use the sqlDataProvider for
               SQL Server because it's optimized specifically for this database. Use the OLE DB provider for other databases.
8.    What is the use of connection object?
·          They are used to connect a data to a command object.
·          An OleDbconnection object is used with an OLEDB provider.
·          A SqlConnection object uses tabular data services (TDS) with MS SQL Server.

9.    What are basic methods of Data adapter?
                  There are three most commonly used methods of Data adapter :
·          Fill
·          Fill Schema
·          Update

10.  What are the two main types of classes associated with errors that are thrown by ADO.NET classes?
                Objects of type sqlError and oleDbError are thrown by the ADO.NET classes.
11.  What method is used by the Command classes to execute SQL statements that return single values?

                 The Execute scalar method executes SQL commands that return single values.
12.  What is the use of command Object?
              There are used to connect connections object to Data reader or data set.
·          Execute Non Query
·          Execute Reader
·          Execute Scalar

13.  Define Execute Non Query?

                Executes the command defined in the command text property against the connection defined in the
               connection property for a query that does not return any row (Insert, Update or Delete).Returns an
               integer indicating the number of rows affected by the query.
14.  Define Execute Reader?
                Executes the command defined in the command text property against the connection defined in the
               connection property.Returns a reader object that in connected to the resulting row set within the
               database, allowing the rows to be retrieved.
15.  Define Execute Scalar?
                Executes the command defined in the command text property against the column defined in the
               connection property.Returns only single value the first column of the first row of the resulting row set
               any other returned columns and rows are discarded.
16.  What are the benefits of ADO.NET?
                There are so many benefits of ADO.NET are
·          Scalability
·          Data Source Independence
·          Interoperability
·          Strongly Typed Fields
·          Performance
17.  What is the use of Data View?

Data View represents a complete table or can be small of rows depending on some criteria. It is the best used for sorting and finding data with in data table.
  
18.  What method in the oleDbDataAdapter class populates a dataset with records?
                 The Fill method populates a dataset with records.
19.  What is Dataset Object?

                 Dataset is a disconnected, in-memory representation of data. It can contain multiple data table from
                different database.
20.  What are the various methods provided by the dataset object to generate XML?
                 There are three methods provided by the dataset object to generate XML are :
·          Read XML
·          GET XML
·          Write XML

21.  What is the difference between dataset clone and copy?

                Dataset Clone : It only copies structure does not copy data.
               Dataset Copy : Copies both structure and data.
22.  What two classes are used to open and connect to a database using ADO.NET?
                 Use the sqlconnection and oleDbConnection classes to connect to a database using ADO.NET.
23.  What is the use of Command builder?
   Command builder builds "parameter" objects automatically. Below is a simple code, which uses commands builder to load its parameter objects.




24.  Name some ADO.NET Objects?
·          Connection Object
·          DataReader Object
·          Command Object
·          DataSet Object
·          DataAdapter Object
25.  How can you populate one Dataset object with data from two different physical databases?

                 Use two connection objects and two Adapter objects. Open a connection to both databases, and then fill
              the same Dataset with the two Adapters.
26.  What are the data access namespaces in .NET?
                 The most common data access namespaces :
·          System. Data
·          System.Data.OleDb
·          System.Data.SQLClient
·          System.Data.SQLTypes
·          System.Data.XML
27.  What is the difference between Dataset and Data reader?
                  Data Reader provides forward only and read only access to data, while the Data set objects can hold more
                 than one table from the same data source as well as the relationships between them.
                 Dataset is a disconnected architecture while data reader is connected architecture. Dataset can persist
                Contents   while data reader cannot persist contents they are forward only.
28.  What is the use of data adapter?
                 This object act as a bridge between data store and dataset.
29.  What two classes are used to execute arbitrary SQL commands in a database using ADO.NET?

                  The Sqlcommand and Oledb command classes are used to execute SQL Commands using ADO.NET.
30.  What is the use of connection object in ado.net?
                The ADO Connection Object is used to create an open connection to a data source. Through this connection,
               you can access and manipulate a database.
31.  What is the difference between ADO.Net Dataset and ADO Record set?
                 ADO.Net Dataset you can retrieve data from two databases like oracle and sql server and merge them in
                one dataset with record set this is not possible. All representation of dataset is using XML while record set
                uses com.
                ADO.Net Record set cannot be transmitted on HTTP while dataset can be.

32.  How arc Row states used in ADO.NET?
                 The DataAdapter class uses Rowstates to extract modified, added, or deleted records.
33.  What is dataset object?
                 The dataset provides the basic for disconnected storage and manipulation of relational data. We fill it from
                a data store, work with it while disconnected from that data store, then reconnect and flush changes back
                 to the data store if required.
34.  What is the use of System.Data namespace in ADO.Net?
                System.Data : This contains the basic objects used for accessing and storing relational data such
               as dataset,datatable and data relation.
35.  What is the use of Sytem.Data.OLEDB namespace in ADO.Net?
                 Sytem.Data.OLEDB : It contains the object that we use to connect to a data source. These objects inherit
                the common base classes and to have the same properties, methods and events as the SqlClient equivalents.
36.  What is the use of System.Data.sqlclient namespace in ADO.Net?
                 System.Data.sqlclient : This contains the objects that we use to connect to a data source .
             This can generally provide better performance as it removes some of the intermediate layers required
             by an OLE-DB connection.
37.  What is the use of System. XML namespace in ADO.Net?
                System. XML : This contains the basic objects required to create read, store, write and manipulate
              XML documents according to W3C recommendations.
38.  What is the preferred method for executing SQL commands that contain parameters?
                The preferred method is to use the sqlParameter and oleDbParameter objects, as detailed in the
              section "Using Parameters with the command Object."
39.  What are the two fundamental objects in ADO.NET?
                 There are two fundamental objects in ADO.NET are : 
               Datareader - connected architecture and 
               Dataset - disconnected architecture.
40.  What is the use of command object?
                         This is the responsible object to use stored procedure.
41.   What .NET tools are used to automatically generate XML Schemas and typed datasets?
               Use either Visual Studio or the XSD.exe tool.

42.  What are different types of Commands available with Data Adapter?
                 The SqlDataAdapter are:
·         Select Command
·         Insert Command
·         Delete Command
·         Update  Command
                     
43.  What is the use of data adapter?
                These objects connect one or more command objects to a Dataset object.
              An OleDb Data Adapter object is used with an OLE-DB provider.
              A Sql Data Adapter object uses Tabular Data Services with MS SQL Server.
44.  What is a Dataset?
                A Dataset is an in memory representation of data loaded from any data source.
45.  What method is used by the command classes to execute commands that do not return result sets, such as the SELECT COUNT command?
               The Execute Non Query method executes SQL commands that don't return a result set.
46.  What are good ADO.NET objects to replace the ADO Recordset object?
DataSet
47.  Why two interfaces can be used to abstract the SQL and OLE DB data providers?

   You can use the IDataReader, IDbCommand, and IDataAdapter classes to abstract the data provider.

48.  What is the difference between "Optimistic" and "Pessimistic" locking?

   In Pessimistic locking when user wants to update data it locks the record and till then no one can update data.
In Optimistic locking multiple users can open the same record for updating, thus increase maximum concurrency.
49.  What is the DataTableCollection?
     An ADO.NET DataSet contains a collection of zero or more tables represented by DataTable objects. The DataTableCollection contains all the DataTable objects in a DataSet.
50.  What providers does Ado.net uses?
            The .NET Framework provides mainly three data providers, they are
·          Microsoft SQL Server
·          OLEDB
·          ODBC



1 comment: