Databases Reference
In-Depth Information
The Microsoft Data Shaping Service for OLE DB
Provides support for the construction of hierarchical (shaped)
Recordset
objects
from one or more data providers. A
hierarchical recordset
is one in which the
value in a particular field can be another
Recordset
object, which would then be
considered a child of the first (parent) recordset.
The Microsoft OLE DB Persistence Provider
Provides support for saving a
Recordset
object to a file and restoring a
Recordset
object from a file.
The Microsoft OLE DB Remoting Provider
Enables a user on a local machine to invoke data providers that reside on a remote
machine.
Actually, an OLE DB service provider is both an OLE DB consumer and an OLE DB
data provider. For example, consider a heterogeneous query processor. (The term
heterogeneous
refers to the fact that the query processor can process queries that
reference data in more than one data source.) When a consumer asks the query processor
to provide data from multiple OLE DB data sources, the query processor acts like a
consumer when it submits the query to multiple data providers and retrieves the data from
the data sources (through each source's data provider), and it acts like a provider when it
returns the results of the query to the consumer that requested the data.
17.4 The ADO Object Model
OLE DB is designed for C programmers. In order to make it accessible to VB
programmers, Microsoft created the ADO object model. This model gives VB
programmers access to certain aspects of the OLE DB paradigm, by allowing the
programmer to program an object model, rather than having to use the OLE DB API
functions directly. For instance, a VB programmer can get access to a data provider by
creating a
Connection
object and setting its Provider property. Thus, the
Connection
object represents a connection to a data store through a data provider.
The ADO object model is actually quite small, even smaller than the DAO object model.
Table 17-1 shows the complete list of ADO objects (along with corresponding collection
objects).
Table 17-1. The ADO objects
C
ommand
C
onnection
E
rror (Errors)
F
ield (Fields)
P
arameter (Parameters)
