5、通过api操作mysql的小例子

#include "stdio.h"
#include "mysql.h"
#include <pthread.h>
#include "stdlib.h"
#include "string"
#include "iostream"

using namespace std;

typedef struct SqlInfo
{
string server;
string user;
string passwd;
string db;
}SqlInfo;

void* showdatabase(void* arg)
{
     SqlInfo *p = (SqlInfo*)arg;

    MYSQL *mysql_test;
    MYSQL_RES *ret;
    MYSQL_ROW row;

// char *server = "localhost";
// char *user = "root";
// char *passwd = "1234"; //伪密码
// char *db = "mysql";
    
    mysql_test = mysql_init(NULL);
if (!mysql_real_connect(mysql_test, p->server.c_str(), p->user.c_str(), p->passwd.c_str(), p->db.c_str(), 0, NULL, 0))
    {
        fprintf(stderr, "%s\n", mysql_error(mysql_test));
return NULL;
    }

if (mysql_query(mysql_test, "show databases"))
    {
        fprintf(stderr, "%s\n", mysql_error(mysql_test));
return NULL;
    }
    ret = mysql_use_result(mysql_test);

    printf("Show Databases:\n");
// while((row = mysql_fetch_row(ret)) != NULL)
// {
// printf("%s\n", row[0]);
// }

//equal to the below
    unsigned int num_fields;
    unsigned int i;

    num_fields = mysql_num_fields(ret);
while ((row = mysql_fetch_row(ret)))
    {
        unsigned long *lengths;
        lengths = mysql_fetch_lengths(ret);
for(i = 0; i < num_fields; i++)
        {
           printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL");
        }
        printf("\n");
    }

    mysql_free_result(ret);
    mysql_close(mysql_test);
} 

int main(int argc, char* argv[])
{
if (argc < 5)
    {
        cout << "Usage: app server user passwd db" << endl;
return -1;
    }

    SqlInfo my_info;
    my_info.server = argv[1];
    my_info.user = argv[2];
    my_info.passwd = argv[3];
    my_info.db = argv[4];

    pthread_t thread1;

    pthread_create(&thread1, NULL, showdatabase, (void*)&my_info);
    pthread_join(thread1,NULL);

return 0;
}