Insert variable into database insert statement

[teppel]

#ifndef __DATABASE_H__
#define __DATABASE_H__

#include <string>
#include <vector>
#include <sqlite3.h>

using namespace std;

class Database
{
public:
Database(char* filename);
~Database();

bool open(char* filename);
vector<vector<string> > query(char* query);
void close();

private:
sqlite3 *database;
};

#endif
==========================================================================
#include "Database.h"
#include <iostream>

Database::Database(char* filename)
{
database = NULL;
open(filename);
}

Database::~Database()
{
}

bool Database::open(char* filename)
{
if(sqlite3_open(filename, &database) == SQLITE_OK)
return true;

return false;
}

vector<vector<string> > Database::query(char* query)
{
sqlite3_stmt *statement;
vector<vector<string> > results;

if(sqlite3_prepare_v2(database, query, -1, &statement, 0) == SQLITE_OK)
{
int cols = sqlite3_column_count(statement);
int result = 0;
while(true)
{
result = sqlite3_step(statement);

if(result == SQLITE_ROW)
{
vector<string> values;
for(int col = 0; col < cols; col++)
{
values.push_back((char*)sqlite3_column_text(statement, col));
}
results.push_back(values);
}
else
{
break;
}
}

sqlite3_finalize(statement);
}

string error = sqlite3_errmsg(database);
if(error != "not an error") cout << query << " " << error << endl;

return results;
}

void Database::close()
{
sqlite3_close(database);
}

===========================================================================

#include <iostream>
#include "Database/Database.h"
using namespace std;
Database *db;
db = new Database("Database.sqlite");
db->query("CREATE TABLE a (a INTEGER, b INTEGER);");
db->query("INSERT INTO a VALUES(1, 2);");
db->query("INSERT INTO a VALUES(5, 4);");
vector<vector<string> > result = db->query("SELECT a, b FROM a;");
for(vector<vector<string> >::iterator it = result.begin(); it < result.end(); ++it)
{
vector<string> row = *it;
cout << "Values: (A=" << row.at(0) << ", B=" << row.at(1) << ")" << endl;
}
db->close();

===========================================================================
Above source extracted from : http://www.dreamincode.net/forums/showtopic122300.htm
I was doing my project and i across the above code. But i am stuck, because after i extract data and wish to put it into database using the variable name, but unable to do so

May i know is it possible to insert into the database using variable name ?
eg.

int i = 100;
db->query("INSERT INTO a VALUES(5, i);");

the above statement prompt me no i columns found

[PanGalactic]

Please edit your post, putting the code inside [code]...[/code] tags.

[yikuang]

this is an example:

char lz_sql[100] ={0};
sprintf(lz_sql, "INSERT INTO a VALUES(5, %d)", i);
//execute sql
//.....