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<h1>ADO OpenSchema Method</h1>
<hr />
<a href="ado_ref_connection.asp"><img class="navup" src="../images/up.gif" alt="Connection Object Reference" border="0" /> Complete Connection Object Reference</a>
<hr />
<p>The OpenSchema method returns a Recordset object with schema information from
the provider about the data source. For example, schema information can include
the names of the tables, names of the columns in the tables, and the data type
of each column. The Recordset will be opened as a read-only recordset.
</p>
<h3>Syntax
</h3>
<table class="ex" cellspacing="0" border="1" width="100%" cellpadding="3">
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<td valign="top">
<pre>Set rs=objconn.OpenSchema(querytype,criteria,schemaid)</pre>
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<table class="ex" cellspacing="0" border="1" width="100%" cellpadding="3">
<tr>
<th align="left" valign="top" width="20%">Parameter</th>
<th align="left" valign="top" width="80%">Description</th>
</tr>
<tr>
<td valign="top">querytype </td>
<td valign="top"> Required. A <a href="#schemaenum">SchemaEnum</a>
value that represents the type of schema query to run<p><b>Note:</b> The
OLEDB specification only require 3 of the SchemaEnum values to be
supported. These are adSchemaTables, adSchemaColumns, and the adSchemaProviderTypes
</p>
</td>
</tr>
<tr>
<td valign="top">criteria </td>
<td valign="top"> Optional. An array of query constraints for each
querytype
option, as listed in <a href="#schemaenum"> SchemaEnum</a>
</td>
</tr>
<tr>
<td valign="top">schemaid </td>
<td valign="top"> The GUID for a provider-schema query not defined by the OLE DB specification.
Required if querytype is set to adSchemaProviderSpecific
</td>
</tr>
</table>
<br />
<hr />
<a name="schemaenum"><h3>SchemaEnum Values</h3></a>
<table class="ex" cellspacing="0" border="1" width="100%" cellpadding="3">
<tr>
<th valign="top" align="left">Constant</th>
<th valign="top" align="left">Value</th>
<th valign="top" align="left">Description</th>
<th valign="top" align="left">Constraint Columns</th>
</tr>
<tr>
<td valign="top">adSchemaProviderSpecific</td>
<td valign="top">-1</td>
<td valign="top">Used if the provider defines its own nonstandard schema
queries</td>
<td valign="top">Provider specific</td>
</tr>
<tr>
<td valign="top">adSchemaAsserts</td>
<td valign="top">0</td>
<td valign="top">Returns the assertions defined in the catalog
</td>
<td valign="top">CONSTRAINT_CATALOG<br />
CONSTRAINT_SCHEMA<br />
CONSTRAINT_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaCatalogs</td>
<td valign="top">1</td>
<td valign="top">Returns the physical attributes associated with catalogs
accessible from the DBMS
</td>
<td valign="top">CATALOG_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaCharacterSets</td>
<td valign="top">2</td>
<td valign="top">Returns the character sets defined in the catalog
</td>
<td valign="top">CHARACTER_SET_CATALOG<br />
CHARACTER_SET_SCHEMA<br />
CHARACTER_SET_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaCollations</td>
<td valign="top">3</td>
<td valign="top">Returns the character collations defined in the catalog
</td>
<td valign="top">COLLATION_CATALOG<br />
COLLATION_SCHEMA<br />
COLLATION_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaColumns</td>
<td valign="top">4</td>
<td valign="top">Returns the columns of tables defined
in the catalog
</td>
<td valign="top">TABLE_CATALOG<br />
TABLE_SCHEMA<br />
TABLE_NAME<br />
COLUMN_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaCheckConstraints</td>
<td valign="top">5</td>
<td valign="top">Returns the check constraints defined in the catalog
</td>
<td valign="top">CONSTRAINT_CATALOG<br />
CONSTRAINT_SCHEMA<br />
CONSTRAINT_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaConstraintColumnUsage</td>
<td valign="top">6</td>
<td valign="top">Returns the columns used by referential constraints,
unique constraints, check constraints, and assertions, defined in the
catalog
</td>
<td valign="top">TABLE_CATALOG<br />
TABLE_SCHEMA<br />
TABLE_NAME<br />
COLUMN_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaConstraintTableUsage</td>
<td valign="top">7</td>
<td valign="top">Returns the tables that are used by referential
constraints, unique constraints, check constraints, and assertions
defined in the catalog
</td>
<td valign="top">TABLE_CATALOG<br />
TABLE_SCHEMA<br />
TABLE_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaKeyColumnUsage</td>
<td valign="top">8</td>
<td valign="top">Returns the columns defined in the catalog that are
constrained as keys
</td>
<td valign="top">CONSTRAINT_CATALOG<br />
CONSTRAINT_SCHEMA<br />
CONSTRAINT_NAME<br />
TABLE_CATALOG<br />
TABLE_SCHEMA<br />
TABLE_NAME<br />
COLUMN_NAME</td>
</tr>
<tr>
<td valign="top">AdSchemaReferentialConstraints</td>
<td valign="top">9</td>
<td valign="top">Returns the referential constraints defined in the
catalog
</td>
<td valign="top">CONSTRAINT_CATALOG<br />
CONSTRAINT_SCHEMA<br />
CONSTRAINT_NAME</td>
</tr>
<tr>
<td valign="top">adSchemaTableConstraints</td>
<td valign="top">10</td>
<td valign="top">Returns the table constraints defined in the catalog
</td>
<td valign="top">CONSTRAINT_CATALOG<br />
CONSTRAINT_SCHEMA<br />
CONSTRAINT_NAME<br />
TABLE_CATALOG<br />
TABLE_SCHEMA<br />
TABLE_NAME<br />
CONSTRAINT_TYPE</td>
</tr>
<tr>
<td valign="top">adSchemaColumnsDomainUsage</td>
<td valign="top">11</td>
<td valign="top">Returns the columns defined in the catalog that are
dependent on a domain defined in the catalog
</td>
<td valign="top">DOMAIN_CATALOG<br />
DOMAIN_SCHEMA<br />
DOMAIN_NAME<br />
COLUMN_NAME</td>
</tr>
<tr>
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