Difference Between Select Query And SelectCommand In Data Adapters

 


Can any one tell me the difference between Select Query and
SelectCommand in data adapters?


 


Using SelectCommand:


 

string selectSQL = "SELECT CustomerID, CompanyName FROM Customers WHERE Country = @Country AND City = @City"; SqlConnection nwindConn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=northwind");SqlDataAdapter custDA = new SqlDataAdapter();           SqlCommand selectCMD = new SqlCommand(selectSQL, nwindConn);custDA.SelectCommand = selectCMD; // Add parameters and set values.selectCMD.Parameters.Add("@Country", SqlDbType.NVarChar, 15).Value = "UK";selectCMD.Parameters.Add("@City", SqlDbType.NVarChar, 15).Value = "London"; DataSet custDS = new DataSet();custDA.Fill(custDS, "Customers");  Using Select Query: 


SqlDataAdapter
da = new SqlDataAdapter("select P_UID,P_EMIAL,P_NAME from p_users where p_email=@p_email
and p_pwd=@p_pwd", con);


            da.SelectCommand.Parameters.Add("@p_email", SqlDbType.VarChar, 50).Value
= etxt1.Text;

            da.SelectCommand.Parameters.Add("@p_pwd", SqlDbType.VarChar, 50).Value = pwdtex.Text;   Can you plz tell vat is the need for giving custDA.SelectCommand and adding parameters to that command instead of  directly giving Select Query in Data Adapter?  Similarly  Update Command: custDA.UpdateCommand.Parameters.Add("@CustomerID", SqlDbType.NChar, 5, "CustomerID") custDA.UpdateCommand.Parameters.Add("@CompanyName", SqlDbType.NVarChar, 40, "CompanyName")Dim myParm As SqlParameter = custDA.UpdateCommand.Parameters.Add("@OldCustomerID", _ SqlDbType.NChar, 5, "CustomerID")myParm.SourceVersion = DataRowVersion.Original[C#]custDA.UpdateCommand.Parameters.Add("@CustomerID", SqlDbType.NChar, 5, "CustomerID"); custDA.UpdateCommand.Parameters.Add("@CompanyName", SqlDbType.NVarChar, 40, "CompanyName"); SqlParameter myParm = custDA.UpdateCommand.Parameters.Add("@OldCustomerID", SqlDbType.NChar, 5, "CustomerID");myParm.SourceVersion = DataRowVersion.Original; instead of above process, y cant v do above method in below procedure? 


private void UpdateStudent(int
RollNo, string SName, string
Course, DateTime Doj, Decimal
FeePaid)


    {


        SqlConnection
conn = new SqlConnection("Data Source=UMASHANKAR\SQLSERVER2005;Initial
Catalog=employee;Persist Security Info=True;User ID=sa;pwd=sa1 ");


 


        SqlCommand
cmd = new SqlCommand("UPDATE Student SET SName='" + SName + "',Course='" + Course + "',Doj='" + Doj + "',FeePaid='" + FeePaid + "'
WHERE RollNo=" + RollNo, conn);


 


        try


        {


            if
(conn.State == ConnectionState.Closed)
conn.Open();


            cmd.ExecuteNonQuery();


        }


        catch {
}


        finally


        {


            cmd.Dispose();


            conn.Close();


            conn.Dispose();


        }


    }


 


PLZ TELL ME
THE DIFFERENCE OR ANY ADVANTAGES OF UPDATECOMMAND PROCESS AND QUERY METHOD

  IN this way I want difference OR ANY ADVANTAGES for InsertCommand, DeleteCommand also