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OpenSchema Method Example (VC++)

This example uses the OpenSchema method to display the name and type of each table in the Pubs database.

// OpenSchemaMethodExample.cpp
// compile with: /EHsc
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")

#include <ole2.h>
#include <stdio.h>
#include <oleauto.h>
#include <conio.h>

// Function declarations
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };
void OpenSchemaX();
void OpenSchemaX2();
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

int main() {
   if ( FAILED(::CoInitialize(NULL)) )
      return -1;

   OpenSchemaX();
   OpenSchemaX2();
   ::CoUninitialize();
}

void OpenSchemaX() {
   // Define ADO object pointers.  Initialize pointers on define.
   // These are in the ADODB::  namespace.
   _ConnectionPtr pConnection = NULL;
   _RecordsetPtr pRstSchema = NULL;

   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");

   try {
      // Open connection.
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
      pConnection->Open (strCnn, "", "", adConnectUnspecified);

      pRstSchema = pConnection->OpenSchema(adSchemaTables);

      while ( !(pRstSchema->EndOfFile) ) {
         _bstr_t table_name = pRstSchema->Fields->GetItem("TABLE_NAME")->Value;

         printf("Table Name: %s\n",(LPCSTR) table_name);

         _bstr_t table_type = pRstSchema->Fields->GetItem("TABLE_TYPE")->Value;

         printf("Table type: %s\n\n",(LPCSTR) table_type);

         pRstSchema->MoveNext();         
      }
   }
   catch (_com_error &e) {
      // Display errors, if any. Pass connection pointer accessed from the Connection.        
      PrintProviderError(pConnection);
      PrintComError(e);
   }

   // Clean up objects before exit.
   if (pRstSchema)
      if (pRstSchema->State == adStateOpen)
         pRstSchema->Close();
   if (pConnection)
      if (pConnection->State == adStateOpen)
         pConnection->Close();
}

void OpenSchemaX2() {
   // Define ADO object pointers. Initialize pointers on define.
   // These are in the ADODB::  namespace.
   _ConnectionPtr pConnection2 = NULL;
   _RecordsetPtr pRstSchema = NULL;

   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");

   try {
      // Open connection.
      TESTHR(pConnection2.CreateInstance(__uuidof(Connection)));
      pConnection2->Open (strCnn, "", "", adConnectUnspecified);

      // Create a safearray which takes four elements,and pass it as 
      // 2nd parameter in OpenSchema method.
      SAFEARRAY FAR* psa = NULL;
      SAFEARRAYBOUND rgsabound;
      _variant_t  var;
      _variant_t  Array;
      rgsabound.lLbound = 0;
      rgsabound.cElements = 4;
      psa = SafeArrayCreate(VT_VARIANT, 1, &rgsabound);
      var.vt = VT_EMPTY;

      long ix;
      ix = 0;
      SafeArrayPutElement(psa, &ix, &var);

      ix= 1;
      SafeArrayPutElement(psa, &ix, &var);

      ix = 2;
      SafeArrayPutElement(psa, &ix, &var);

      var.vt = VT_BSTR;
      char * s1 = "VIEW";
      _bstr_t str = s1;
      var.bstrVal = str;

      ix = 3;
      SafeArrayPutElement(psa, &ix, &var);

      Array.vt = VT_ARRAY|VT_VARIANT;
      Array.parray = psa;  

      pRstSchema = pConnection2->OpenSchema(adSchemaTables,&Array);

      while(!(pRstSchema->EndOfFile))
      {
         printf("Table Name: %s\n", 
            (LPCSTR) (_bstr_t) pRstSchema->Fields->GetItem("TABLE_NAME")->Value);

         printf("Table type: %s\n\n",
            (LPCSTR) (_bstr_t) pRstSchema->Fields->GetItem("TABLE_TYPE")->Value);

         pRstSchema->MoveNext();         
      }
   }    // End Try statement.
   catch (_com_error &e) {
      // Display errors, if any. Pass connection pointer accessed from the Connection.
      PrintProviderError(pConnection2);
      PrintComError(e);
   }

   // Clean up objects before exit.
   if (pRstSchema)
      if (pRstSchema->State == adStateOpen)
         pRstSchema->Close();
   if (pConnection2)
      if (pConnection2->State == adStateOpen)
         pConnection2->Close();
}

void PrintProviderError(_ConnectionPtr pConnection) {
   // Print Provider Errors from Connection object.
   // pErr is a record object in the Connection's Error collection.
   ErrorPtr pErr = NULL;

   if ( (pConnection->Errors->Count) > 0) {
      long nCount = pConnection->Errors->Count;
      // Collection ranges from 0 to nCount -1.
      for ( long i = 0 ; i < nCount ; i++ ) {
         pErr = pConnection->Errors->GetItem(i);
         printf("\t Error number: %x\t%s", pErr->Number, pErr->Description);
      }
   }
}

void PrintComError(_com_error &e) {
   _bstr_t bstrSource(e.Source());
   _bstr_t bstrDescription(e.Description());

   // Print COM errors. 
   printf("Error\n");
   printf("\tCode = %08lx\n", e.Error());
   printf("\tCode meaning = %s\n", e.ErrorMessage());
   printf("\tSource = %s\n", (LPCSTR) bstrSource);
   printf("\tDescription = %s\n", (LPCSTR) bstrDescription);
}
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