CПАСИБО ХАРЬКОВУ ЗА ДЕТАЛЬНЫЙ ОТВЕТ, НО ПОЧЕМУ ERROR ?
В примере в MSDN на функцию “SQLAllocHandle()” ERROR , почему?

SQLHENV henv = SQL_NULL_HENV;
SQLHDBC hdbc = SQL_NULL_HDBC;
SQLHSTMT hstmt = SQL_NULL_HSTMT;

RETCODE retcode;

/*Allocate environment handle */
retcode = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);

if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) {
/* Set the ODBC version environment attribute */
retcode = SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0);

if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) {
/* Allocate connection handle */
retcode = SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc);

if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) {
/* Set login timeout to 5 seconds. */
//- SQLSetConnectAttr(hdbc, (SQLPOINTER)SQL_LOGIN_TIMEOUT, 5, 0);

//- SQLSetConnectAttr(hdbc, (void*)SQL_LOGIN_TIMEOUT, 5, 0);
//ODBC and SQL Server



/*- SQLSetConnectAttr(hdbc, (void*)SQL_LOGIN_TIMEOUT, 5, 0);
error C2664: 'SQLSetConnectAttr' : cannot convert parameter 2 from 'void *' to 'long' */
//- SQLSetConnectAttr(hdbc, (int *)SQL_LOGIN_TIMEOUT, 5, 0);

//- SQLSetConnectAttr(hdbc, (int *)SQL_LOGIN_TIMEOUT,(long)15, 0);
//- SQLSetConnectAttr(hdbc, (long *)SQL_LOGIN_TIMEOUT, 15, 0);

/* Connect to data source */
retcode = SQLConnect(hdbc, (SQLCHAR*) "Sales", SQL_NTS,
(SQLCHAR*) "JohnS", SQL_NTS,
(SQLCHAR*) "Sesame", SQL_NTS);

if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO){
/* Allocate statement handle */
retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt);

if (retcode == SQL_SUCCESS || retcode == SQL_SUCCESS_WITH_INFO) {
/* Process data */
;
;
;

SQLFreeHandle(SQL_HANDLE_STMT, hstmt);
}
SQLDisconnect(hdbc);
}
SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
}
}
SQLFreeHandle(SQL_HANDLE_ENV, henv);