Riferimento al database locale di SQL Server ExpressSQL Server Express LocalDB Reference

In questa sezione sono contenute informazioni sul database locale di SQL Server Express:This section contains information about the SQL Server Express LocalDB:

Codice di esempioCode Sample

Nell'esempio seguente viene illustrata l'API LocalDB.The following sample demonstrates the LocalDB API. Prima di eseguire questo esempio, verificare che LocalDB sia installata nel computer in uso.Make sure that LocalDB is installed on the computer before running this sample. È possibile installare LocalDB dal programma di installazione di SQL Server 2017SQL Server 2017 Express.You can install LocalDB from setup in the SQL Server 2017SQL Server 2017 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 sqlncli.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 "sqlncli.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();  
}