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(Language C++) Variables in mysql_query???
Posted by: Christopher Zeman
Date: November 16, 2006 11:43AM

I am writing a small program in C++ that accepts data on a socket connection from SBC's. The SBC's send data in the following format: Unit Name,1,2. 1 is the unit number, and 2 is the number of cycles on that unit.

I want to automatically create a table for each Unit Name that I receive. Here is what I have so far:
#include "ServerSocket.h"
#include "SocketException.h"
#include <string>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <mysql/mysql.h>

int main ( int argc, int argv[] )
{
	try
    	{
      		// Create the socket
      		ServerSocket server ( 14036 );
		while ( true )
		{
			ServerSocket new_sock;
			server.accept ( new_sock );

			try
	    		{
	      			while ( true )
				{
		  			std::string data;
		  			new_sock >> data;
		  			new_sock << data;
		  			using namespace std;
		  			string trainid(data);

		  			std::string unit_name, unit_num, num_cycles;
					std::string::size_type pos = trainid.find(',');
		  			if (pos != std::string::npos)
		  			{
		      				ride = trainid.substr(0,pos);
		      				cout << unit_name << endl;
		  			}

   		  			trainid = trainid.substr(pos+1);
		  			pos = trainid.find(',');
	   	  			if (pos != std::string::npos)
		   			{
		      				unit_num = trainid.substr(0,pos);
		      				cout << unit_num << endl;
		   			}

		   			num_cycles = trainid.substr(pos+1);
		   			cout << num_cycles << endl;
			
					MYSQL db_conn;
  					MYSQL_RES *result;
					MYSQL_ROW row;
					MYSQL_FIELD *fields;
					unsigned int numrows;
					unsigned int numfields;
					int c;
					char user[] = "user";
					char password[] = "password";
					char host[] = "localhost";
					char dbname[] = "TrainID";
					char buffer[BUFSIZ];

					mysql_init(&db_conn);
					
					// Attempt to connect to the database.
					if (mysql_real_connect(&db_conn, host, user, password, dbname, 0, NULL, 0) == NULL)
					{
						fprintf(stderr, "Could not connect to mysql server.  Error %s\n", mysql_error(&db_conn));
					}
		
					// Create a table for the ride if it doesn't already exist.
					string create_table1 = "CREATE TABLE ";
					string create_table2 = " (Unit INT PRIMARY KEY, Cycles BIGINT);";
					string create_table3 = create_table1 + unit_name + create_table2;
					
					if (!mysql_query(&db_conn, create_table3) == 0)
					{
						fprintf(stderr, "Could not create the table.  Error %s\n", mysql_error(&db_conn));
					}			
				}
	    		}
	  		catch ( SocketException& ) {}
		}
	}

catch ( SocketException& e )
	{
      		std::cout << "Exception was caught:" << e.description() << "\nExiting.\n";
    	}

return 0;
}


I try to compile and get the following error:
[root@automation Devel]# make
g++    -c -o ServerSocket.o ServerSocket.cpp
g++    -c -o Socket.o Socket.cpp
g++    -c -o TrainID.o TrainID.cpp
TrainID.cpp: In function `int main(int, int*)':
TrainID.cpp:76: error: cannot convert `std::string' to `const char*' for argument `2' to `int mysql_query(MYSQL*, const char*)'
make: *** [TrainID.o] Error 1

I understand what is happening here, but what do I need to do? I can't seem to find an answer. Am I going to run into the same thing when I try to insert values into my columns?

Thanks! :)
Chris

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(Language C++) Variables in mysql_query???
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