MDAC 2.5 SDK - ADO

Microsoft OLE DB Provider for ODBC

See Also

To an ADO or RDS programmer, an ideal world would be one in which every data source exposes an OLE DB interface, so that ADO could call directly into the data source. Although increasingly more database vendors are implementing OLE DB interfaces, some data sources are not yet exposed this way. However, virtually all DBMS systems in use today can be accessed through ODBC.

ODBC drivers are available for every major DBMS in use today, including Microsoft SQL Server™, Microsoft Access (Microsoft Jet database engine), and Microsoft FoxPro®, in addition to non-Microsoft database products such as Oracle.

The Microsoft ODBC Provider, however, allows ADO to connect to any ODBC data source. The provider is free-threaded and unicode enabled.

The provider supports transactions, although different DBMS engines offer different types of transaction support. For example, Microsoft Access supports nested transactions up to five levels deep.

This is the default provider for ADO, and all provider-dependent ADO properties and methods are supported.

Connection String Parameters

To connect to this provider, set the Provider= argument of the ConnectionString property to:

MSDASQL

Reading the Provider property will return this string as well.

Typical Connection String

A typical connection string for this provider is:

"Provider=MSDASQL;DSN=dsnName;UID=userName;PWD=userPassword;"

Consisting of these keywords:

Because this is the default provider for ADO, if you omit the Provider= parameter from the connection string, ADO will attempt to establish a connection to this provider.

The provider does not support any specific connection parameters in addition to those defined by ADO. However, the provider will pass any non-ADO connection parameters to the ODBC driver manager.

Because you can omit the Provider parameter, you can therefore compose an ADO connection string that is identical to an ODBC connection string for the same data source. Use the same parameter names (DRIVER=, DATABASE=, DSN=, and so on), values, and syntax as you would when composing an ODBC connection string. You can connect with or without a predefined data source name (DSN) or FileDSN.

Syntax with a DSN or FileDSN:

"[Provider=MSDASQL;] { DSN=name | FileDSN=filename } ; [DATABASE=database;] UID=user; PWD=password"

Syntax without a DSN (DSN-less connection):

"[Provider=MSDASQL;] DRIVER=driver; SERVER=server; DATABASE=database; UID=user; PWD=password"

If you use a DSN or FileDSN, it must be defined through the ODBC Data Source Administrator in the Windows Control Panel. In Microsoft Windows 2000, the ODBC Administrator is located under Administrative Tools. In previous versions of Windows, the ODBC Administrator icon is named 32-bit ODBC or simply ODBC.

As an alternative to setting a DSN, you can specify the ODBC driver (DRIVER=), such as "SQL Server;" the server name (SERVER=); and the database name (DATABASE=).

You can also specify a user account name (UID=), and the password for the user account (PWD=) in the ODBC-specific parameters or in the standard ADO-defined User ID and Password parameters.

Although a DSN definition already specifies a database, you can specify a DATABASE parameter in addition to a DSN to connect to a different database. It is a good idea to always include the DATABASE parameter when you use a DSN. This will ensure that you connect to the proper database in the event that another user changed the default database parameter since you last checked the DSN definition.

Provider-Specific Connection Properties

The OLE DB provider for ODBC adds several properties to the Properties collection of the Connection object. The following table lists these properties with the corresponding OLE DB property name in parentheses.

Provider-Specific Recordset and Command Properties

The OLE DB provider for ODBC adds several properties to the Properties collection of the Recordset and Command objects. The following table lists these properties with the corresponding OLE DB property name in parentheses.

Command Text

How you use the Command object largely depends on the data source, and what type of query or command statement it will accept.

ODBC provides a specific syntax for calling stored procedures. For the CommandText property of a Command object, the CommandText argument to the Execute method on a Connection object, or the Source argument to the Open method on a Recordset object, passes in a string with this syntax:

"{ [ ? = ] call procedure [ ( ? [, ? [ , … ]] ) ] }"

Each ? references an object in the Parameters collection. The first ? references Parameters(0), the next ? references Parameters(1), and so on.

The parameter references are optional and depend on the structure of the stored procedure. If you want to call a stored procedure that defines no parameters, your string would look like this:

"{ call procedure }"

If you have two query parameters, your string would look like this:

"{ call procedure ( ?, ? ) }"

If the stored procedure will return a value, the return value is treated as another parameter. If you have no query parameters but you do have a return value, your string would look like this:

"{ ? = call procedure }"

Finally, if you have a return value and two query parameters, your string would look like this:

"{ ? = call procedure ( ?, ? ) }"

Recordset Behavior

The following tables list the standard ADO methods and properties available on a Recordset object opened with this provider.

For more detailed information about Recordset behavior for your provider configuration, run the Supports method and enumerate the Properties collection of the Recordset to determine whether provider-specific dynamic properties are present.

Availability of standard ADO Recordset properties:

The AbsolutePosition and AbsolutePage properties are write-only when ADO is used with version 1.0 of the Microsoft OLE DB Provider for ODBC.

Availability of standard ADO Recordset methods:

*Not supported for Microsoft Access databases.

Dynamic Properties

The Microsoft OLE DB Provider for ODBC inserts several dynamic properties into the Properties collection of the unopened Connection, Recordset, and Command objects.

The tables below are a cross-index of the ADO and OLE DB names for each dynamic property. The OLE DB Programmer's Reference refers to an ADO property name by the term, "Description." You can find more information about these properties in the OLE DB Programmer's Reference. Search for the OLE DB property name in the Index or see Appendix C: OLE DB Properties.

Connection Dynamic Properties

The following properties are added to the Connection object's Properties collection.

Recordset Dynamic Properties

The following properties are added to the Recordset object's Properties collection.

Command Dynamic Properties

The following properties are added to the Command object's Properties collection.

See Also   For details regarding specific implementation and functional information about the Microsoft OLE DB Provider for ODBC, consult the documentation for Microsoft OLE DB Provider for ODBC and the Microsoft OLE DB Programmer'sReference available in the MDAC SDK or visit the Universal Data Access Web site.