Riferimento al database locale di SQL Server Express

Si applica a: SQL Server

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

• Informazioni di riferimento sui messaggi di errore di SQL Server Express LocalDB

• Informazioni si riferimento sull'API dell'istanza di SQL Server Express LocalDB

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();  
}