1、问题缘由
前两天看视频学习数据库操作时候，使用C++ 连接语句调用 SQL sever 2019怎么也无法调用成功，但本人的错误愿意比较低级，各位高手一般不会犯。但是憋了两天查资料还是查到很多东西，在这里跟大家分享一下。
2、连接测试
首先使用VS2017数据库链接工具直接链接SQL server进行测试，如下图所示，点击连接到数据库
之后选择Microsoft SQL Server作为数据源。
之后进行服务器名称(即主机名称)的填写，选择身份验证方式为SQL Server身份验证，填写创建数据库时候的用户名和密码，选择要进行连接的数据库名称。
之后点击测试连接，出现下面的界面即连接成功！
3、寻找连接字符串语句
打开服务器资源管理器
打开SQLServer对象资源管理器
在SQLServer对象资源管理器中打开想要调用的数据库的属性
在属性中便可以找到连接字符串了
4、几种可以连接成功的连接字符串
4.1 较早版本
"Driver=SQL Server;Server=%s;Database=%s;UID=%s;PWD=%s;"
4.2新版本
其中server表示服务器名称，Database表示数据库名称，UID表示用户名，PSD表示密码
"Provider='SQLOLEDB'; Data Source=%s ; Initial Catalog=%s;User ID=%s;Password=%s;"
其中Data Source表示服务器名称，Initial Catalog表示数据库名称，User ID表示用户名，Password表示密码
4.3 官网给出的示例
即上述新版本所述，官网连接如下：
5、 最简单的连接代码
下面根据SQL server 2019 官方文档示例，给出最简单的连接代码。
_ConnectionPtr pRstAuthors = NULL; _bstr_t strCnn("Provider='SQLOLEDB'; Data Source='LAPTOP-CRSKGRNV'; Initial Catalog='worker';User ID=sa;Password=123456;"); pRstAuthors.CreateInstance(__uuidof(Connection)); pRstAuthors->Open(strCnn, User ID, Password, adModeUnknown);
其中User ID和Password需要根据自己的情况进行修改，连接字符串中是本人的信息，大家也需要根据自己的信息和上述字段解释进行相应的修改，上述完整的代码可以到官网进行copy测试，下面给出官网测试代码和链接：
PS.上述链接代码和下述官网示例本人只在32位系统上跑通了，在64位系统会连接不上，原因本人没有搞清楚，有清楚的大神还烦请指点一下，[抱拳了]。
// BeginSaveCpp.cpp // compile with: /EHsc #import "msado15.dll" no_namespace rename("EOF", "EndOfFile") #include <ole2.h> #include <stdio.h> #include <conio.h> #include <io.h> // Function declarations inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); }; bool FileExists(); void SaveX1(); void SaveX2(); void SaveX3(); void PrintProviderError(_ConnectionPtr pConnection); void PrintComError(_com_error &e); int main() { if ( FAILED(::CoInitialize(NULL)) ) return -1; // If File exists in the specified directory, then display error if (!FileExists()) { SaveX1(); SaveX2(); SaveX3(); } ::CoUninitialize(); } // First, access and save the authors table. void SaveX1() { HRESULT hr = S_OK; // Define ADO object pointers. Initialize pointers on define. // These are in the ADODB:: namespace. _RecordsetPtr pRstAuthors = NULL; // Definitions of other variables _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source' ; Initial Catalog='pubs'; Integrated Security='SSPI';"); try { TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset))); pRstAuthors->Open("SELECT * FROM authors",strCnn, adOpenDynamic, adLockBatchOptimistic, adCmdText); // For sake of illustration, save the Recordset to a diskette in XML format. pRstAuthors->Save("c:\\pubs.xml", adPersistXML); } catch(_com_error &e) { // Notify the user of errors, if any. // Pass a connection pointer accessed from the Recordset. _variant_t vtConnect = pRstAuthors->GetActiveConnection(); // GetActiveConnection returns connect string if connection // is not open, else returns Connection object. switch(vtConnect.vt) { case VT_BSTR: PrintComError(e); break; case VT_DISPATCH: PrintProviderError(vtConnect); break; default: printf("Errors occured."); break; } } if (pRstAuthors) if (pRstAuthors->State == adStateOpen) pRstAuthors->Close(); } // At this point, you have arrived at your destination. // You will access the authors table as a local, disconnected Recordset. // Don't forget you must have the MSPersist provider on the machine you // are using in order to access the saved file, c:\pubs.xml. void SaveX2() { HRESULT hr = S_OK; // Define ADO object pointers. Initialize pointers on define. // These are in the ADODB:: namespace. _RecordsetPtr pRstAuthors = NULL; try { TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset))); // For sake of illustration, we specify all parameters. pRstAuthors->Open("c:\\pubs.xml", "Provider='MSPersist';", adOpenForwardOnly, adLockBatchOptimistic, adCmdFile); // Now you have a local, disconnected Recordset. // (In this example, changes will not be saved). pRstAuthors->Find("au_lname = 'Carson'", NULL, adSearchForward); if (pRstAuthors->EndOfFile) { printf("Name not found ...\n"); pRstAuthors->Close(); return; } pRstAuthors->GetFields()->GetItem("City")->PutValue("Chicago"); pRstAuthors->Update(); // Save changes in ADTG format this time, purely for sake of illustration. // Note that the previous version is still on the diskette as c:\pubs.xml. pRstAuthors->Save("c:\\pubs.adtg", adPersistADTG); } catch(_com_error &e){ // Notify the user of errors if any. // Pass a connection pointer accessed from the Recordset. _variant_t vtConnect = pRstAuthors->GetActiveConnection(); // GetActiveConnection returns connect string if connection // is not open, else returns Connection object. switch(vtConnect.vt) { case VT_BSTR: PrintComError(e); break; case VT_DISPATCH: PrintProviderError(vtConnect); break; default: printf("Errors occured."); break; } } if (pRstAuthors) if (pRstAuthors->State == adStateOpen) pRstAuthors->Close(); } // Now update the database with changes. void SaveX3() { HRESULT hr = S_OK; // Define ADO object pointers. Initialize pointers on define. // These are in the ADODB:: namespace. _RecordsetPtr pRstAuthors = NULL; _ConnectionPtr pCnn = NULL; // Definitions of other variables _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';"); try { TESTHR(pCnn.CreateInstance(__uuidof(Connection))); TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset))); // If there is no ActiveConnection, you can open with defaults. pRstAuthors->Open("c:\\pubs.adtg", "Provider=MSPersist;", adOpenForwardOnly, adLockBatchOptimistic, adCmdFile); // Connect to the database, associate the Recordset with the connection, // then update the database table with the changed Recordset. pCnn->Open(strCnn, "", "", NULL); pRstAuthors->PutActiveConnection(_variant_t((IDispatch *) pCnn)); pRstAuthors->UpdateBatch(adAffectAll); } catch(_com_error &e) { // Notify the user of errors if any. // Pass a connection pointer accessed from the Recordset. _variant_t vtConnect = pRstAuthors->GetActiveConnection(); // GetActiveConnection returns connect string if connection // is not open, else returns Connection object. switch(vtConnect.vt) { case VT_BSTR: PrintComError(e); break; case VT_DISPATCH: PrintProviderError(vtConnect); break; default: printf("Errors occured."); break; } } if (pRstAuthors) if (pRstAuthors->State == adStateOpen) pRstAuthors->Close(); if (pCnn) if (pCnn->State == adStateOpen) pCnn->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("Error number: %x\t%s\n", pErr->Number, (LPCSTR) 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); } bool FileExists() { struct _finddata_t xml_file; long hFile; if( (hFile = _findfirst("c:\\pubs.xml", &xml_file )) != -1L) { printf( "File already exists!\n" ); return(true); } else return (false); }
SQL server 2019官网连接示例，链接
