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 ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

＃i nclude ;

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