Params keyword is used to accept variable number of parameters.

Yes, it is possible to load multiple tables in a single dataset.29. Which provider is used to connect MS Access, Oracle, etc.?

OLEDB Provider and ODBC Provider are used to connect to MS Access and Oracle. Oracle Data Provider is also used to connect exclusively for oracle database.

With respect to usage, there is no difference between OLEDB Provider and SqlClient. The difference lies in their performance. SqlClient is explicitly used to connect your application to SQL server directly, OLEDB Provider is generic for various databases, such as Oracle and Access including SQL Server.

ADO.NET is a very important feature of .NET Framework, which is used to work with data that is stored in structured data sources, such as databases and XML files. The following are some of the important features of ADO.NET:

Contains a number of classes that provide you with various methods and attributes to manage the communication between your application and data source.

Enables you to access different data sources, such as Microsoft SQL Server, and XML, as per your requirements.

Datareader and Dataset

The most important section in ADO.NET architecture is “Data Provider”. Data Provider provides access to data source (SQL SERVER, ACCESS, ORACLE).
Connection.
Command object(This is the responsible object to use stored procedures)
Data Adapter(This object acts as a bridge between datastore and dataset).
Datareader(This object reads data from data store in forward only mode).

using Dataset.Clear() method you can clear all the data from DataSet

It is an in-Memory cache of data retrieved from Data Source.

Execute Reader
Execute Reader will be used to return the set of rows, on execution of SQL Query or Stored procedure using command object.

Execute Scalar
Execute Scalar will be used to return the single value, on execution of SQL Query or Stored procedure using command object.

Execute Non Query
If the command or stored procedure performs INSERT, DELETE or UPDATE operations, then we use Execute Non Query method. Execute Non Query method returns an integer specifying the number of rows inserted, deleted or updated.

Create a connection to the database using a connection object.
Open the Database Connection.
Invoke a command to create a Dataset object using an adapter object.
Use the Dataset object in code to display data or to change items in the database.
Invoke a command to update the database from the Dataset object using an adapter object.
Close the database connection.