Using the Command Object

After connecting to a data source, you need to execute requests against it to obtain result sets. ADO encapsulates this type of command functionality in the Command object.

You can use the Command object to request any type of operation from the provider, assuming that the provider can interpret the command string properly. A common operation for data providers is to query a database and return records in a Recordset object. Recordsets will be discussed later in this and other chapters; for now, think of them as tools to hold and view result sets. As with many ADO objects, depending on the functionality of the provider, some Command object collections, methods, or properties might generate errors when referenced.

It is not always necessary to create a Command object to execute a command against a data source. You can use the Execute method on the Connection object or the Open method on the Recordset object. However, you should use a Command object if you need to reuse a command in your code or if you need to pass detailed parameter information with your command. These scenarios are covered in more detail later in this chapter.

Note   Certain Commands can return a result set as a binary stream or as a single Record rather than as a Recordset, if this is supported by the provider. Also, some Commands are not intended to return any result set at all (for example, a SQL Update query). This chapter will cover the most typical scenario, however: executing Commands that return results into a Recordset object. For more information about returning results into Records or Streams, see Chapter 10: Records and Streams.