OpenSchema Method

Obtains database schema information from the provider.

Syntax

Set recordset = connection.OpenSchema (QueryType, Criteria, SchemaID)

Return Values

Returns a Recordset object that contains schema information. The Recordset will be opened as a read-only, static cursor. The QueryType determines what columns appear in the Recordset.

Parameters

QueryType

Any SchemaEnum value that represents the type of schema query to run.

Criteria

Optional. An array of query constraints for each QueryType option, as listed in SchemaEnum.

SchemaID

The GUID for a provider-schema query not defined by the OLE DB specification. This parameter is required if QueryType is set to adSchemaProviderSpecific; otherwise, it is not used.

Remarks

The OpenSchema method returns self-descriptive information about the data source, such as what tables are in the data source, the columns in the tables, and the data types supported.

The QueryType argument is a GUID that indicates the columns (schemas) returned. The OLE DB specification has a full list of schemas.

The Criteria argument limits the results of a schema query. Criteria specifies an array of values that must occur in a corresponding subset of columns, called constraint columns, in the resulting Recordset.

The constant adSchemaProviderSpecific is used for the QueryType argument if the provider defines its own nonstandard schema queries outside those listed above. When this constant is used, the SchemaID argument is required to pass the GUID of the schema query to execute. If QueryType is set to adSchemaProviderSpecific but SchemaID is not provided, an error will result.

Providers are not required to support all of the OLE DB standard schema queries. Specifically, only adSchemaTables, adSchemaColumns, and adSchemaProviderTypes are required by the OLE DB specification. However, the provider is not required to support the Criteria constraints listed above for those schema queries.

Remote Data Service Usage   The OpenSchema method is not available on a client-side Connection object.

Note   In Visual Basic, columns that have a four-byte unsigned integer (DBTYPE UI4) in the Recordset returned from the OpenSchema method on the Connection object cannot be compared to other variables. For more information about OLE DB data types, see Chapter 13 and Appendix A of the Microsoft OLE DB Programmer's Reference.

See Also

Visual Basic Example | Visual C++ Example | Visual J++ Example

Open Method (ADO Connection) | Open Method (ADO Record) | Open Method (ADO Recordset) | Open Method (ADO Stream) | Appendix A: Providers

Applies To: Connection Object