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Display Column and Catalog Metadata for Sparse Columns (OLE DB)

This sample creates a table with three columns: a sparse column, a column that is not a sparse column, and a columnset column. The sample then displays OLE DB flags showing the column and catalog metadata for the non-sparse column and the columnset column.

This sample works with SQL Server 2008 or later. For more information about sparse columns, see Sparse Columns Support in SQL Server Native Client.

Make sure your INCLUDE environment variable includes the directory that contains sqlncli.h.

#include <stddef.h>
#include <comdef.h>
#include <msdasc.h>
#include <sqlncli.h>

#define CHECKED(_hr) \
   do { \
      if (FAILED(hr =_hr)) { \
         PrintHR(hr); \
         goto ERR; \
      } \
   } while (0)

#define CHECK_NOT_NULL(x) \
   do { \
      if((x) == NULL) { \
         PrintHR(E_OUTOFMEMORY); \
         goto ERR; \
      } \
   } while(0)

#define SAFE_RELEASE(pI) \
   do { \
      if (pI) { \
         pI->Release(); \
         pI = 0; \
      } \
   } while(0)

#define PROVIDER_FREE(pv) \
   do { \
      if (pv) { \
         CoTaskMemFree(pv); \
         pv = NULL; \
      } \
   } while(0)

#define PRINT_FLAGS(f,m) \
   do { \
      if ((f & m) == m) \
         wprintf(L"%ls, ", L#m); \
   } while(0)

#define PrintHR(hr) PrintHR_internal(hr, __FILE__, __LINE__)


#define CHECKED3(_hr,_Obj,_IID) \
   do { \
      if (FAILED(hr = _hr)) { \
         DumpErrorInfo(_Obj,_IID); \
         goto ERR; \
      } \
   } while(0)

void PrintHR_internal(HRESULT hr, char * szFile, ULONG uLine) {
   wprintf(L"Error HR = %d (%x) %hs(%d)\n", hr, hr, szFile, uLine);
}

// DumpErrorInfo queries error interfaces, retrieving available status or error information.
void DumpErrorInfo ( IUnknown* pObjectWithError, REFIID IID_InterfaceWithError ) {
   // Interfaces used in the example.
   IErrorInfo * pIErrorInfoAll = NULL;
   IErrorInfo * pIErrorInfoRecord = NULL;
   IErrorRecords * pIErrorRecords = NULL;
   ISupportErrorInfo * pISupportErrorInfo = NULL;
   ISQLErrorInfo * pISQLErrorInfo = NULL;
   ISQLServerErrorInfo * pISQLServerErrorInfo = NULL;

   // Number of error records.
   ULONG nRecs;
   ULONG nRec;

   // Basic error information from GetBasicErrorInfo.
   ERRORINFO errorinfo;

   // IErrorInfo values.
   BSTR bstrDescription;
   BSTR bstrSource;

   // ISQLErrorInfo parameters.
   BSTR bstrSQLSTATE;
   LONG lNativeError;

   // ISQLServerErrorInfo parameter pointers.
   SSERRORINFO * pSSErrorInfo = NULL;
   OLECHAR * pSSErrorStrings = NULL;

   // Hard-code an American English locale for the example.
   DWORD MYLOCALEID = 0x0409;

   // Only ask for error information if the interface supports it.
   if (FAILED(pObjectWithError->QueryInterface(IID_ISupportErrorInfo, (void**) &pISupportErrorInfo))) {
      wprintf(L"SupportErrorErrorInfo interface not supported\n");
      return;
   }

   if (FAILED(pISupportErrorInfo->InterfaceSupportsErrorInfo(IID_InterfaceWithError))) {
      wprintf(L"InterfaceWithError interface not supported\n");
      return;
   }

   // Do not test the return of GetErrorInfo. It can succeed and return
   // a NULL pointer in pIErrorInfoAll. Simply test the pointer.
   GetErrorInfo(0, &pIErrorInfoAll);

   if (pIErrorInfoAll != NULL) {
      // Test to see if it's a valid OLE DB IErrorInfo interface exposing a list of records.
      if (SUCCEEDED(pIErrorInfoAll->QueryInterface(IID_IErrorRecords, (void**) &pIErrorRecords))) {
         pIErrorRecords->GetRecordCount(&nRecs);

         // Within each record, retrieve information from each of the defined interfaces.
         for (nRec = 0; nRec < nRecs; nRec++) {
            // From IErrorRecords, get the HRESULT and a reference to the ISQLErrorInfo interface.
            pIErrorRecords->GetBasicErrorInfo(nRec, &errorinfo);
            pIErrorRecords->GetCustomErrorObject(nRec,IID_ISQLErrorInfo, (IUnknown**) &pISQLErrorInfo);

            // Display the HRESULT, then use the ISQLErrorInfo.
            wprintf(L"HRESULT:\t%#X\n", errorinfo.hrError);

            if (pISQLErrorInfo != NULL) {
               pISQLErrorInfo->GetSQLInfo(&bstrSQLSTATE, &lNativeError);

               // Display the SQLSTATE and native error values.
               wprintf(L"SQLSTATE:\t%s\nNative Error:\t%ld\n", bstrSQLSTATE, lNativeError);

               // SysFree BSTR references.
               SysFreeString(bstrSQLSTATE);

               // Get the ISQLServerErrorInfo interface from ISQLErrorInfo before releasing the reference.
               pISQLErrorInfo->QueryInterface( IID_ISQLServerErrorInfo, (void**) &pISQLServerErrorInfo); 

               pISQLErrorInfo->Release();
            }

            // Test to ensure the reference is valid, then get error information from ISQLServerErrorInfo.
            if (pISQLServerErrorInfo != NULL) {
               pISQLServerErrorInfo->GetErrorInfo(&pSSErrorInfo, &pSSErrorStrings);

               // ISQLServerErrorInfo::GetErrorInfo succeeds even when it has nothing to return. 
               // Test the pointers before using.
               if (pSSErrorInfo) {
                  // Display the state and severity from the returned information. 
                  // The error message comes from IErrorInfo::GetDescription.
                  wprintf(L"Error state:\t%d\nSeverity:\t%d\n", pSSErrorInfo->bState, pSSErrorInfo->bClass);

                  // IMalloc::Free needed to release references on returned values.
                  CoTaskMemFree(pSSErrorStrings);
                  CoTaskMemFree(pSSErrorInfo);
               }

               pISQLServerErrorInfo->Release();
            }

            if (SUCCEEDED(pIErrorRecords->GetErrorInfo(nRec, MYLOCALEID, &pIErrorInfoRecord))) {
               // Get the source and description (error message) from the record's IErrorInfo.
               pIErrorInfoRecord->GetSource(&bstrSource);
               pIErrorInfoRecord->GetDescription(&bstrDescription);

               if (bstrSource != NULL) {
                  wprintf(L"Source:\t\t%s\n", bstrSource);
                  SysFreeString(bstrSource);
               }

               if (bstrDescription != NULL) {
                  wprintf(L"Error message:\t%s\n", bstrDescription);
                  SysFreeString(bstrDescription);
               }

               pIErrorInfoRecord->Release();
            }
         }
         pIErrorRecords->Release();
      }
      else {
         // IErrorInfo is valid; get the source and description to see what it is.
         pIErrorInfoAll->GetSource(&bstrSource);
         pIErrorInfoAll->GetDescription(&bstrDescription);

         if (bstrSource != NULL) {
            wprintf(L"Source:\t\t%s\n", bstrSource);
            SysFreeString(bstrSource);
         }

         if (bstrDescription != NULL) {
            wprintf(L"Error message:\t%s\n", bstrDescription);
            SysFreeString(bstrDescription);
         }
      }

      pIErrorInfoAll->Release();
   }
   else 
      wprintf(L"GetErrorInfo has not returned ErrorInfo.\n");

   pISupportErrorInfo->Release();
   return;
}

void Test_GetRowset(IDBSchemaRowset *pdbSchemaRowset, DBCOUNTITEM cExpectedRows) {
   HRESULT hr;
   IRowset * pRowset = NULL;
   IAccessor * pAccessor = NULL;
   HACCESSOR hAccessor = NULL;

   struct sRowData {
      wchar_t wszColumnName [128];
      VARIANT_BOOL fIsSparse;
      VARIANT_BOOL fIsColumnSet;
   } rowData;

   DBBINDING rgBindings[3] = {
      {4, offsetof(sRowData, wszColumnName), 0, 0, 0, 0, 0,
      DBPART_VALUE,DBMEMOWNER_CLIENTOWNED, DBPARAMIO_NOTPARAM, sizeof(rowData.wszColumnName),0, DBTYPE_WSTR, 0, 0},
      {41, offsetof(sRowData, fIsSparse),0, 0, 0, 0, 0,
      DBPART_VALUE,DBMEMOWNER_CLIENTOWNED, DBPARAMIO_NOTPARAM, sizeof(rowData.fIsSparse),   0, DBTYPE_BOOL, 0, 0},
      {42, offsetof(sRowData, fIsColumnSet),0, 0, 0, 0, 0,
      DBPART_VALUE,DBMEMOWNER_CLIENTOWNED, DBPARAMIO_NOTPARAM, sizeof(rowData.fIsColumnSet),0, DBTYPE_BOOL, 0, 0}
   };

   DBCOUNTITEM iRow;
   BSTR bstrTable = SysAllocString(L"tbl_sparse_test");

   CHECK_NOT_NULL(bstrTable);

   tagVARIANT rgRestrictions[3];
   VariantInit(rgRestrictions);
   VariantInit(rgRestrictions+1);
   VariantInit(rgRestrictions+2);
   rgRestrictions[0].vt = VT_EMPTY;
   rgRestrictions[1].vt = VT_EMPTY;
   rgRestrictions[2].vt = VT_BSTR;
   rgRestrictions[2].bstrVal = bstrTable;

   wprintf(L"\nTesting %ls\n",  cExpectedRows == 3 ? L"DBSCHEMA_COLUMNS_EXTENDED" : L"DBSCHEMA_SPARSE_COLUMN_SET");

   CHECKED(pdbSchemaRowset->GetRowset( 
      NULL,
      cExpectedRows == 3 ?
      DBSCHEMA_COLUMNS_EXTENDED: DBSCHEMA_SPARSE_COLUMN_SET,
      3,
      rgRestrictions,
      IID_IRowset,
      0,
      NULL,
      (IUnknown**)&pRowset)
      );

   DBCOUNTITEM cRowsObtained = 0;
   HROW rgRows[3];
   HROW * pRows = rgRows;

   CHECKED(pRowset->GetNextRows( 0, 0, cExpectedRows, &cRowsObtained, &pRows));

   if (cRowsObtained != cExpectedRows) 
      CHECKED(E_UNEXPECTED);

   CHECKED(pRowset->QueryInterface(IID_IAccessor, (void**)&pAccessor));
   CHECKED(pAccessor ->CreateAccessor( DBACCESSOR_ROWDATA, 3, rgBindings, sizeof(rowData), &hAccessor, NULL));

   for (iRow = 0 ; iRow < cExpectedRows; iRow++) {
      CHECKED(pRowset->GetData( rgRows[iRow], hAccessor, (void*)&rowData));

      wprintf(L"Column %ls,\tIsSparse=%ls, \tIsColumnSet=%ls\n",
         rowData.wszColumnName,
         (rowData.fIsSparse    ? L"TRUE " : L"FALSE"),
         (rowData.fIsColumnSet ? L"TRUE " : L"FALSE"));
   }

ERR:
   if (bstrTable) 
      SysFreeString(bstrTable);
   SAFE_RELEASE(pAccessor);
   SAFE_RELEASE(pRowset);
}

int __cdecl main() {
   HRESULT hr;
   IDBInitialize * pIDBInit = NULL;
   IDataInitialize * pIDI = NULL;
   IDBCreateSession * pIDBCreateSession = NULL;
   IDBCreateCommand * pIDBCreateCommand = NULL;
   ICommandText * pCommand = NULL;
   IDBSchemaRowset * pdbSchemaRowset = NULL;
   IOpenRowset * pOpenRowset = NULL;
   IColumnsInfo * pColumnsInfo = NULL;
   ULONG cSchemas;
   ULONG cFoundSchemas = 0;
   GUID * rgSchemas = NULL;
   ULONG * rgRestSupport = NULL;
   DBID dbidSparse;
   DBORDINAL cColumns, i;
   WCHAR * pNameBuff = NULL;
   DBCOLUMNINFO * prgColInfo = NULL;

   CHECKED(CoInitializeEx(NULL, COINIT_MULTITHREADED));
   CHECKED(CoCreateInstance(CLSID_MSDAINITIALIZE, NULL, CLSCTX_INPROC_SERVER, IID_IDataInitialize, (void**)&pIDI));
   CHECKED(pIDI->GetDataSource(NULL, CLSCTX_INPROC_SERVER, L"Provider=SQLNCLI11; Integrated Security=SSPI; Data Source=.; Initial Catalog=tempdb", IID_IDBInitialize, (IUnknown**)&pIDBInit));
   CHECKED(pIDBInit->Initialize());
   CHECKED(pIDBInit->QueryInterface(IID_IDBCreateSession, (void**)&pIDBCreateSession));
   CHECKED(pIDBCreateSession->CreateSession(NULL, IID_IDBCreateCommand, (IUnknown**)&pIDBCreateCommand));
   CHECKED(pIDBCreateCommand->CreateCommand(NULL, IID_ICommandText, (IUnknown**)&pCommand));

   // Drop the old table if it exists
   CHECKED(pCommand->SetCommandText(DBGUID_DBSQL, L"if object_id('tempdb.dbo.tbl_sparse_test','U') is not null drop table tempdb.dbo.tbl_sparse_test"));
   CHECKED(pCommand->Execute(NULL, IID_NULL, NULL, NULL, NULL));

   // Create a new table
   CHECKED(pCommand->SetCommandText(DBGUID_DBSQL, L"create table tempdb.dbo.tbl_sparse_test (col1 int SPARSE, col2 int, col3 XML column_set for all_sparse_columns)"));
   CHECKED3(pCommand->Execute(NULL, IID_NULL, NULL, NULL, NULL), pCommand, IID_ICommandText);

   // Insert a row into the table
   CHECKED(pCommand->SetCommandText(DBGUID_DBSQL, L"insert tempdb.dbo.tbl_sparse_test (col1, col2) values (1,2)"));
   CHECKED3(pCommand->Execute(NULL, IID_NULL, NULL, NULL, NULL), pCommand, IID_ICommandText);

   // Let's check the schemas support
   CHECKED(pIDBCreateCommand->QueryInterface(IID_IDBSchemaRowset, (void**)&pdbSchemaRowset));
   CHECKED(pdbSchemaRowset->GetSchemas(&cSchemas, &rgSchemas, &rgRestSupport));

   while (cSchemas--) {
      if (rgSchemas[cSchemas]== DBSCHEMA_COLUMNS_EXTENDED ||
         rgSchemas[cSchemas]== DBSCHEMA_SPARSE_COLUMN_SET) {
         if (++cFoundSchemas == 2)
            break;
      }
   }

   if (cFoundSchemas != 2) {
      wprintf(L"Found %d of expected 2 new DBSCHEMAs\n", cFoundSchemas);
      goto ERR;
   }

   // Test the schemas:
   Test_GetRowset(pdbSchemaRowset, 1);
   Test_GetRowset(pdbSchemaRowset, 3);

   // Test the column info
   CHECKED(pIDBCreateCommand->QueryInterface(IID_IOpenRowset, (void**)&pOpenRowset));

   dbidSparse.eKind = DBKIND_NAME;
   dbidSparse.uName.pwszName = L"tbl_sparse_test";

   // This will result in "select * from tbl_sparse_test"
   CHECKED(pOpenRowset->OpenRowset( NULL, &dbidSparse, NULL, IID_IColumnsInfo, 0, NULL, (IUnknown**)&pColumnsInfo));

   CHECKED(pColumnsInfo->GetColumnInfo(&cColumns, &prgColInfo, &pNameBuff));
   wprintf(L"\nTesting GetColumnInfo:\n");

   for ( i = 0 ; i < cColumns ; i++) {
      wprintf(L"Column name: %ls, flags: ",prgColInfo[i].pwszName);
      DWORD dwFlags = prgColInfo[i].dwFlags;
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_ISFIXEDLENGTH);
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_WRITEUNKNOWN);
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_WRITE);
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_MAYBENULL);
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_ISLONG);
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_ISNULLABLE);
      PRINT_FLAGS(dwFlags, DBCOLUMNFLAGS_SS_ISCOLUMNSET);

      wprintf(L"\n");
   }

ERR:
   PROVIDER_FREE(prgColInfo);
   PROVIDER_FREE(pNameBuff);
   SAFE_RELEASE(pColumnsInfo);
   SAFE_RELEASE(pOpenRowset);
   PROVIDER_FREE(rgSchemas);
   PROVIDER_FREE(rgRestSupport);
   SAFE_RELEASE(pdbSchemaRowset);
   SAFE_RELEASE(pCommand);
   SAFE_RELEASE(pIDBCreateCommand);
   SAFE_RELEASE(pIDBCreateSession);
   SAFE_RELEASE(pIDI);
   SAFE_RELEASE(pIDBInit);
   CoUninitialize();
}
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