what is mysql c api? Parse mysql c api simple application

#include <stdio.h>
#include <stdlib.h>
#include "mysql.h"
int insert_new_table(MYSQL *sock1,const char *row1,const char *row2)
{
	char buf[128];
	sprintf(buf,"insert into aaa.tmp (num,name) VALUES(%s,&#39;%s&#39;)",row1,row2);
	mysql_query(sock1,buf);
	printf("----\n");
    return 0;
}


int main(int argc,char **argv)
{
        MYSQL mysql,*sock;
        MYSQL_RES *res;
	MYSQL_FIELD *fd;
	MYSQL_ROW row;
	char qbuf[160];

	//init mysql
        mysql_init(&mysql);
	sock = mysql_real_connect(&mysql,"localhost","root","root","tmp",0,NULL,0);
	if(sock == 0)
	{
	    fprintf(stderr,"connect mysql db %s\n",mysql_error(&mysql));
        exit(1);
	}	
	sprintf(qbuf,"select id,username,groupname from usergroup;");
	
	if(mysql_query(sock,qbuf)){
	     fprintf(stderr,"query error %s\n",mysql_error(sock));
         exit(1);
	 }
	 
	 if(!(res = mysql_store_result(sock)))
	 {
	     exit(1);
	 }
         printf("number of fields returned :%d\n",mysql_num_fields(res));
	 int i=0;
	 while((row = mysql_fetch_row(res)) != NULL)
	 {
	     printf("%s,%s,%s\n",row[i],row[i+1],row[i+2]);
//           insert_new_table(sock,row[i],row[i+1]);       //insert
	 }
	 mysql_free_result(res);
	 mysql_close(sock);
	 return 0;
}