c连接mysql数据库实例

c连接mysql数据库实例

连接数据库test 用户名root密码abc
在里面有一个username的表，describe username结果如下
mysql>; describe username;
+---------------+-----------------+--------+-------+---------+----------+
| Field           | Type              | Null    | Key   | Default | Extra   |
+---------------+-----------------+--------+-------+---------+----------+
| id                | int(10)           | YES   |          | NULL    |             |
| username   | varchar(32)   |           | PRI    |             |             |
+---------------+-----------------+--------+-------+---------+----------+

mysql>; select * from username;
+------+--------------+
| id     | username |
+------+--------------+
|     1   | sfs             |
+------+--------------+
1 row in set (0.00 sec)


本文目的查找执行select id from username这个语句并打印结果

CODE:＃i nclude <unistd.h>;
＃i nclude <arpa/inet.h>;
＃i nclude <stdio.h>;
＃i nclude <stdlib.h>;
＃i nclude <string.h>;
＃i nclude <sys/types.h>;
＃i nclude <sys/socket.h>;
＃i nclude <netinet/in.h>;
＃i nclude <mysql/mysql.h>;
＃i nclude <signal.h>;
＃i nclude <errno.h>;
＃i nclude <syslog.h>;
MYSQL mysql;
main()
{
         char host[32]="localhost";
         char user[32]="root";
         char passwd[32]="abc";
         char dbname[32]="test";        
        
         if( mysql_init(&mysql) == NULL )
         {
                 syslog(LOG_USER|LOG_INFO,"inital mysql handle error\n");
                 return 1;
         }
         if (mysql_real_connect(&mysql,host,user,passwd,dbname,0,NULL,0) == NULL)
         {
                 syslog(LOG_USER|LOG_INFO, "Failed to connect to database: Error: %s\n",mysql_error(&mysql));
                 return 1;
         }
         else syslog(LOG_USER|LOG_INFO, "connect to database: \n");
         find_ps();        
         db_close();
         return 0;
}
int db_close()
{
         mysql_close(&mysql);
          return 0;
}


int   find_ps ()
{
         MYSQL_ROW m_row;
         MYSQL_RES *m_res;
         char sql[1024],username[32];
         int res=1;
         int *id;
         sprintf(sql,"select id from username");
         if(mysql_query(&mysql,sql) != 0)
         {
                 syslog(LOG_USER|LOG_INFO, "select ps_info Error: %s\n",mysql_error(&mysql));
                 return res;
         }
         m_res = mysql_store_result(&mysql);
         if(m_res==NULL)
         {
                 syslog(LOG_USER|LOG_INFO, "select username Error: %s\n",mysql_error(&mysql));
                 res = 3;
                 return res;
         }
         if(m_row = mysql_fetch_row(m_res))
         {
                 printf("m_row=%d\n",atoi(m_row[0]));
                 res = 0;                
         }
         mysql_free_result(m_res);
         return res;
}

编译命令
gcc -g connect_db.c -L/usr/lib/mysql -lmysqlclient -lz
注意：
如果/tmp/ccTGmMS21.o: In function `main':
/tmp/ccTGmMS21.o(.text+0x11): undefined reference to `mysql_init'
那么参数增加-L/usr/lib/mysql -lmysqlclient 
如果
usr/lib/mysql/libmysqlclient.a(my_compress.o): In function `my_uncompress':
my_compress.o(.text+0xaa): undefined reference to `uncompress'
那么增加-lz参数