What is the use of Command objects?

They are used to connect a Connection object to a DataReader or DataSet. Following are the methods provided by aCommand object:

• ExecuteNonQuery
Executes the command defined in the CommandText property against the connection defined in theConnection property for a query that does not return any row (an UPDATE, DELETE, or INSERT). Returns an Integer indicating the number of rows affected by the query.

• ExecuteReader
Executes the command defined in the CommandText property against the connection defined in theConnection property. Returns a "reader" object that is connected to the resulting row set within the database, allowing the rows to be retrieved.

• ExecuteScalar
Executes the command defined in the CommandText property against the connection defined in theConnection property. Returns only a single value (effectively the first column of the first row of the resulting row set, any other returned columns and rows are discarded). It is fast and efficient when only a "singleton" value is required.