insert multiple char * into a const char* with pre filled text - c++

Question

i have setup a working mysql connector for my c++ project. Now i'm making a login for registered users.
i want to get the username and password into the SQLquery string.
i am trying to get this working:
currently its displaying noting and the game crashes.
#include "boost/lexical_cast.hpp" //boost
#include <cgl\cgl.h> // game library (core media library)
#include <sstream> // sstream
char* username=DEFSER;
char* password=PASS12345;
const char *SQLquery;
std::string SQLquery("SELECT * FROM Users WHERE UserName='" + boost::lexical_cast<std::string>(username) + "' AND PassWord='" + boost::lexical_cast<std::string>(password) + "'");
what i want to get out of SQLquery:
SELECT * FROM Users WHERE UserName='DEFSER' AND PassWord='PASS12345'
and i execute it in this way:
res = stmt->executeQuery(SQLquery);
this is not a fully working code i only want to know how i can get the username and password into the SQLquery.
error when i try to run the query:
Run-Time Check Failure #3 - The variable 'SQLquery' is being used without being initialized.

Answer 1

What you are doing is not concatenating strings, you are adding std::string objects to a literal string pointer.
The std::string class handles concatenation of C-style strings just fine without any lexical_cast, so just do e.g.
std::string SQLquery = "SELECT * FROM Users WHERE UserName='" +
username + "' AND PassWord='" + password + "'";
After testing the above solution doesn't actually work for me. But the following does:
std::string SQLQuery = (std::ostringstream() << "SELECT * FROM Users WHERE UserName='"
<< username << "' AND PassWord='" << password << "'").str();