how to connect c++ with sql

[Ansari Bros]

I’m making a project in my last year of bsc-it, and I’m using c++ and sql language. Is it possible to make connection between this two language, if yes then how. I don’t know much about this connection. Please give me the step by step procedure of connection, I’ve never done connection in any language. give me the easiest procedure for connection. I need your help.

[Enriqueta]

Well, I’m not sure about the c++ connection with sql but try this code:
CDatabase cdb;
CString sDBName = _T("DBQ=your database name");
CString sUserDSN = _T("ODBC;DSN=your sql DSN name found in ODBC Data Source- User DSN tab");
CString sSQLStmt = _T("your sql statement");

cdb.OpenEx( sUserDSN + ";" + sDBName, CDatabase::noOdbcDialog );

CRecordset rsTemp(&cdb);
rsTemp.Open(CRecordset::dynaset, sSQLStmt);

This is the ODBC way. Hope it work for you.

[Elieis]

You need to write following code in your program for connection:
BOOL MyApp::ConnectToDatabase(CString szLogonUser,
CString szUserPass, CString szServer,
int nTrustedConnection)
{
m_pConnDdmData = NULL;
CString szddmdata = "";
int nVersion = 0, nTimeout = 30;

//OLE DB Provider for SQL Server 2000
if(DATABASEPROVIDER == SQL2000PROVIDER)
{
nTimeout = theApp.GetProfileInt(
"SERVER CONNECTION SETTINGS","CONNECTION TIMEOUT",15);
if((nTimeout < 15) || (nTimeout > 999)) nTimeout = 15;

// Standard user that uses SQL Server Authentication
if(nTrustedConnection == 1)
{
strCnn = "Provider=SQLOLEDB;Data Source=";
strCnn += szServer;
strCnn += ";Initial Catalog=ddmdata;Trusted_Connection=yes;";
}
else
{
strCnn = "Provider=SQLOLEDB;Data Source=";
strCnn += szServer;
strCnn += ";Initial Catalog=ddmdata;";
strCnn += "User ID="; //jim2000;Password=password";
strCnn += szLogonUser;
strCnn += ";Password=";
strCnn += szUserPass;
}
}

try
{
theApp.TESTHR(m_pConnDdmData.CreateInstance(__uuidof(Connection)));
m_pConnDdmData->ConnectionTimeout = nTimeout; //60;
HRESULT hr = m_pConnDdmData->Open((_bstr_t)strCnn,"","",
adConnectUnspecified);
_bstr_t version = m_pConnDdmData->Version;

szddmdata = (LPCSTR)version;
szddmdata.Remove('.');
nVersion = atoi(szddmdata);
if(nVersion < 26)
{
CString sztext;
sztext.Format("The Microsoft Data Access Components version "
"must be at least version 2.6! You must update your "
"MDAC Components from version %s.",(LPCSTR)version);

MessageBox(NULL,sztext,"Terminating the DDM Program",
MB_OK);
return FALSE;
}
}
catch(_com_error &e)
{
if(m_pConnDdmData != NULL)
m_pConnDdmData.Release();
m_pConnDdmData = NULL;
AfxMessageBox("DDMDATA Database connection error!\nDescription: "
+ (_bstr_t)e.Description());
return FALSE;
}
//_bstr_t szConnectstring = m_pConnDdmData->GetConnectionString();
return TRUE;
}
The above code will allow your program to connect to a database.

[mesterio]

If you want to connect your c++ program to a sql database, than you have to create a odbc connection for accessing database.
Here are procedures or rather steps used in the C++ coding for connecting to a database:
• Include Header Files
• Open a Connection to a Database
• Choose an ODBC Driver
• Query the Database
• Creating an ODBC Statement Object
• Executing a Query and Returning an ODBCResultSet Object
• Extracting Data from an ODBCResultSet

[mv]

The connection of c++ program to database are explain step by step. To make aconnection follow the steps:
1). Include the Header Files

# include statements at the beginning of your programs:
#include <sql.h>
#include<sqltypes.h>
#include<sqlext.h>

2). Open a Connection to a Database

Set the environment handle:
SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &hdlEnv);
Set ODBC Driver version:
SQLSetEnvAttr(hdlEnv,SQL_ATTR_ODBC_VERSION,(void*)SQL_OV_ODBC30);
Set the connection handle:
SQLAllocHandle(SQL_HANDLE_DBC, hdlEnv, &hdlConn);
Connect to the database:
SQLConnect(hdlConn, (SQLCHAR*)dsnName,SQL_NTS,(SQLCHAR*)userID,SQL_NTS, (SQLCHAR*)passwd, SQL_NTS);

3). Choose Driver

•DSN – Data Source Name
•Open the GUI ODBC Administrator (ODBCConfig)
•Choose the appropriate ODBC driver
•Provide a meaningful name to the DSN
•Specify the server and the host string (host string is required if the server is running on a different machine)

4). Query the Database

Querying the database involves the following steps:
–Creating a Statement
SQLAllocHandle(SQL_HANDLE_STMT, hdlDbc, &hdlStmt);
It allocates the memory for the statement handle. The database handle obtained during connection phase is passed as the second argument.
– Executing a Query
SQLExecDirect(hdlStmt, stmt, SQL_NTS);
It executes the query, which is passed in as SQLCHAR* in the second argument.

5). Extract the Data out of the Executed Query

SQLGetData(hStmt,colNum,type,retVal,buffLength,&cbData);
It extracts data from table as void* data and places it in retVal
colNum refers to the column number provided in the SELECT statement in SQLExecDirect()
Type is one of the standard ODBC data types
example: DT_STRING Ã* for a string data type
DT_DOUBLE Ã* for a double data type
buffLength is the estimated size of the expected data
cbData is the actual size of the data

6). Traverse Through the Results

SQLFetch(hStmt);
Fetches the next record
hStmt is the statement handle obtained using SQLAllocHandle
If a record is available, It returns SQL_SUCCEEDED

7). Close the Statement and the Connection

SQLFreeHandle(SQL_HANDLE_STMT, hdlStmt);
It closes and de-allocates the memory reserved for the statement handle
SQLFreeHandle(SQL_HANDLE_DBC, hdlConn);
It disconnects and de-allocates the memory reserved for the connection handle
SQLFreeHandle(SQL_HANDLE_ENV, hdlEnv);
It de-allocates the memory occupied by the environment handle


the above code will connect your c++ program with a sql database.

[Ernesto4]

For creating connection between your frontend and backend which is c++ and sql you need to write the following code:
//Header files:
02
03 #include <sql.h>
04 #include<sqltypes.h>
05 #include<sqlext.h>
06 ...
07 ....
08
09 //Declaration:
10
11 SQLHandle hdlEnv, hdlConn, hdlStmt, hdlDbc
12 char* stmt = "SELECT * from NutHead" NutHead is the Table name; //SQL statement
13
14 //for example
15 name of your program or what ever…..char *dsnName = “COLLECTORâ€�
16 char* userID = "eXceed";
17 char* passwd = "hole";
18 char* retVal[256];
19 unsigned int cbData;
20
21 SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &hdlEnv);
22 SQLSetEnvAttr(hdlEnv,SQL_ATTR_ODBC_VERSION,(void*)SQL_OV_ODBC30);
23 SQLAllocHandle(SQL_HANDLE_DBC, hdlEnv, &hdlConn);
24 SQLConnect(hdlConn, (SQLCHAR*)dsnName,SQL_NTS,(SQLCHAR*)userID,SQL_NTS, (SQLCHAR*)passwd, SQL_NTS);
25 SQLAllocHandle(SQL_HANDLE_STMT, hdlDbc, &hdlStmt);
26 SQLExecDirect(hdlStmt, (SQLCHAR*)stmt, SQL_NTS);
27
28
29 //Initialize the database connection
30
31 while(SQLFetch(hdlStmt) == SQL_SUCCEEDED)
32 {
33 SQLGetData(hdlStmt,0,DT_STRING,retVal,256,&cbData);
34 std::cout << retVal << std::endl;
35 }
36 SQLFreeHandle(SQL_HANDLE_STMT, hdlStmt);
37 SQLFreeHandle(SQL_HANDLE_DBC, hdlConn);
38 SQLFreeHandle(SQL_HANDLE_ENV, hdlEnv); //End the connection

The above code is a example of connecting c++ with database.