mysql
今天给新来的同事做mysql培训，用到的一个例子：
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
代码:
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
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 errorn");
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: %sn",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: %sn",mysql_error(&mysql));
return res;
}
m_res = mysql_store_result(&mysql);
if(m_res==NULL)
{
syslog(LOG_USER|LOG_INFO, "select username Error: %sn",mysql_error(&mysql));
res = 3;
return res;
}
if(m_row = mysql_fetch_row(m_res))
{
printf("m_row=%dn",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
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