1.Returns a datareader with data.
2.It is done by command object.
3.It is readonly.
4.It executes only select command.
5. This is known as a forward-only retrieval of records.It uses your sql statement to read through the table from the first to the last.
1.Returns the recordset as a XML document.
2. Just Like Reader other than this
1.It will not return any data.
2.It is used with insert ,update and delete.
3.It returns only the number of rows affected.
1.It returns only one value.
2.That value will the first column first row value.
3.This is very light-weight and is perfect when all your query asks for is one item.
4. Select Count(*) or with in group by function
1.Its for command objects.
2.It returns the value given by database through select statement.