Riferimento al database locale di SQL Server Express

  • Articolo

Si applica a: SQL Server

In questa sezione sono contenute informazioni sul database locale di SQL Server Express:

Codice di esempio

Nell'esempio seguente viene illustrata l'API LocalDB. Prima di eseguire questo esempio, verificare che LocalDB sia installata nel computer in uso. È possibile installare LocalDB dal programma di installazione in SQL Server Express.

// compile with: Advapi32.lib  
#include <SDKDDKVer.h>  
#include <stdio.h>  
  
// To use LocalDB API, you must define LOCALDB_DEFINE_PROXY_FUNCTIONS before you include msoledbsql.h in one (and only one) of the   
// source files in your program. LOCALDB_DEFINE_PROXY_FUNCTIONS causes code to be generated that binds to the LocalDB API at runtime.  
  
#define LOCALDB_DEFINE_PROXY_FUNCTIONS  
#include "msoledbsql.h"  
  
HRESULT CreateAndStartLocalDBInstance(PWCHAR wszVersion, PWCHAR wszInstanceName) {  
   HRESULT hr;  
  
   if (SUCCEEDED(hr = LocalDBCreateInstance(wszVersion, wszInstanceName, 0)))  
      hr = LocalDBStartInstance(wszInstanceName, 0, NULL, NULL);  
  
   return hr;  
}  
  
HRESULT StopAndDeleteLocalDBInstance(PWCHAR wszInstanceName) {  
   HRESULT hr;  
  
   if (SUCCEEDED(hr = LocalDBStopInstance(wszInstanceName, 0, 30)))   // 30 seconds timeout   
      hr = LocalDBDeleteInstance(wszInstanceName, 0);  
  
   return hr;  
}  
  
void PrintLocalDBError(HRESULT hr) {  
   HRESULT hrError;  
   WCHAR wszMessage[1024];  
   DWORD dwMessage = 1024;  
  
   if (hr == LOCALDB_ERROR_NOT_INSTALLED)  
      wprintf(L"Local DB is not installed.\n");  
  
   else if (hr == LOCALDB_ERROR_CANNOT_LOAD_RESOURCES)  
      wprintf(L"Cannot load resources for Local DB API DLL. Local DB installation is corrupted.\n");  
  
   else if (FAILED(hrError = LocalDBFormatMessage(hr, 0, 0, wszMessage, &dwMessage)))  
      wprintf(L"Cannot format an error message for a Local DB error code: %#x. LocalDBFormatMessage returned: %#x\n", hr, hrError);  
  
   else  
      wprintf(L"%s\n", wszMessage);  
}  
  
HRESULT PrintLocalDBInstances() {  
   HRESULT hr;  
   DWORD dwNumberOfInstances = 0;  
  
   if (FAILED(hr = LocalDBGetInstances(NULL, &dwNumberOfInstances)))  
      if (hr != LOCALDB_ERROR_INSUFFICIENT_BUFFER)  
         return hr;  
  
   PTLocalDBInstanceName localDBInstnces = (PTLocalDBInstanceName) malloc(dwNumberOfInstances * sizeof(TLocalDBInstanceName));  
   if (localDBInstnces == NULL) {  
      return HRESULT_FROM_WIN32(ERROR_OUTOFMEMORY);  
   }  
  
   if (FAILED(hr = LocalDBGetInstances(localDBInstnces, &dwNumberOfInstances))) {  
      free(localDBInstnces);  
      return hr;  
   }  
  
   for (DWORD i = 0; i < dwNumberOfInstances; i++) {  
      LocalDBInstanceInfo localDBInstanceInfo;  
  
      if (FAILED(hr = LocalDBGetInstanceInfo(localDBInstnces[i], &localDBInstanceInfo, sizeof(localDBInstanceInfo)))) {  
         free(localDBInstnces);  
         return hr;  
      }  
  
      wprintf(L"Name: %s State: %s Version: %u.%u.%u.%u\n",  
         localDBInstnces[i],   
         localDBInstanceInfo.bIsRunning ? L"running" : L"stopped",  
         localDBInstanceInfo.dwMajor,  
         localDBInstanceInfo.dwMinor,  
         localDBInstanceInfo.dwBuild,  
         localDBInstanceInfo.dwRevision);  
   }  
  
   free(localDBInstnces);  
   return S_OK;  
}  
  
int main() {  
   HRESULT hr;  
  
   WCHAR wszInstanceName[] = L"Contoso";  
   WCHAR wszVersion[] = L"11.0";  
  
   if (FAILED(hr = CreateAndStartLocalDBInstance(wszVersion, wszInstanceName)))  
      PrintLocalDBError(hr);  
  
   PrintLocalDBInstances();  
  
   if (FAILED(hr = StopAndDeleteLocalDBInstance(wszInstanceName)))  
      PrintLocalDBError(hr);  
  
   PrintLocalDBInstances();  
}