linux下用C语言对mysql中select语句的封装

1.需要用到mysql c api

2.步骤通常是：连接数据库，执行查询，异常处理这些。

3.你需要对api 进行一些了解，然后合理调用。

参考代码：

//连接代码：

/*

* connect1.c - connect to and disconnect from MySQL server

*/

#include <my_global.h>

#include <my_sys.h>

#include <mysql.h>

static char *opt_host_name = NULL /* server host (default=localhost) */

static char *opt_user_name = NULL /* username (default=login name) */

static char *opt_password = NULL /* password (default=none) */

static unsigned int opt_port_num = 0 /* port number (use built-in value) */

static char *opt_socket_name = NULL /* socket name (use built-in value) */

static char *opt_db_name = NULL /* database name (default=none) */

static unsigned int opt_flags = 0 /* connection flags (none) */

static MYSQL *conn/* pointer to connection handler */

int

main (int argc, char *argv[])

{

/* initialize connection handler */

conn = mysql_init (NULL)

if (conn == NULL)

{

fprintf (stderr, "mysql_init() failed (probably out of memory)\n")

exit (1)

}

/* connect to server */

if (mysql_real_connect (conn, opt_host_name, opt_user_name, opt_password,

opt_db_name, opt_port_num, opt_socket_name, opt_flags) == NULL)

{

fprintf (stderr, "mysql_real_connect() failed\n")

mysql_close (conn)

exit (1)

}

/* disconnect from server */

mysql_close (conn)

exit (0)

}

//处理sql 语句的函数：

void

process_statement (MYSQL *conn, char *stmt_str)

{

MYSQL_RES *res_set

if (mysql_query (conn, stmt_str) != 0) /* the statement failed */

{

print_error (conn, "Could not execute statement")

return

}

/* the statement succeededdetermine whether it returned data */

res_set = mysql_store_result (conn)

if (res_set) /* a result set was returned */

{

/* process rows and then free the result set */

process_result_set (conn, res_set)

mysql_free_result (res_set)

}

else /* no result set was returned */

{

/*

* does the lack of a result set mean that the statement didn't

* return one, or that it should have but an error occurred?

*/

if (mysql_field_count (conn) == 0)

{

/*

* statement generated no result set (it was not a SELECT,

* SHOW, DESCRIBE, etc.)just report rows-affected value.

*/

391

Processing SQL Statements

printf ("%lu rows affected\n",

(unsigned long) mysql_affected_rows (conn))

}

else /* an error occurred */

{

print_error (conn, "Could not retrieve result set")

}

}

}

//以上提供的是常规的处理，你需要根据实际情况完善。

//同时调用了一些mysql 的api函数。

ref:

MySQL

(Fourth Edition)

Paul DuBois

php封装mysql类

复制代码

代码如下:

<?php

class

Mysql

{

private

$host

private

$user

private

$pwd

private

$dbName

private

$charset

private

$conn

=

null

public

function

__construct()

{

$this->host

=

'localhost'

$this->user

=

'root'

$this->pwd

=

'root'

$this->dbName

=

'test'

$this->connect($this->host,$this->user,$this->pwd)

$this->switchDb($this->dbName)

$this->setChar($this->charset)

}

//负责链接

private

function

connect($h,$u,$p)

{

$conn

=

mysql_connect($h,$u,$p)

$this->conn

=

$conn

}

//负责切换数据库

public

function

switchDb($db)

{

$sql

=

'use'

.

$db

$this->query($sql)

}

//负责设置字符集

public

function

setChar($char)

{

$sql

=

'set

names'

.

$char

$this->query($sql)

}

//负责发送sql查询

public

function

query($sql)

{

return

mysql_query($sql,$this->conn)

}

//负责获取多行多列的select结果

public

function

getAll($sql)

{

$list

=

array()

$rs

=

$this->query($sql)

if

(!$rs)

{

return

false

}

while

($row

=

mysql_fetch_assoc($rs))

{

$list[]

=

$row

}

return

$list

}

public

function

getRow($sql)

{

$rs

=

$this->query($sql)

if(!$rs)

{

return

false

}

return

mysql_fetch_assoc($rs)

}

public

function

getOne($sql)

{

$rs

=

$this->query($sql)

if

(!$rs)

{

return

false

}

return

mysql_fetch_assoc($rs)

return

$row[0]

}

public

function

close()

{

mysql_close($this->conn)

}

}

echo

'<pre>'

$mysql

=

new

Mysql()

print_r($mysql)

$sql

=

"insert

into

stu

values

(4,'wangwu','99998')"

if($mysql->query($sql)){

echo

"query成功"

}else

{

echo

"失败"

}

echo

"<br

/>"

$sql

=

"select

*

from

stu"

$arr

=

$mysql->getAll($sql)

print_r($arr)

?>

复制代码

代码如下:

<?php

/*

MYSQL

数据库访问封装类

MYSQL

数据访问方式，php4支持以mysql_开头的过程访问方式，php5开始支持以mysqli_开头的过程和mysqli面向对象

访问方式，本封装类以mysql_封装

数据访问的一般流程：

1,连接数据库

mysql_connect

or

mysql_pconnect

2,选择数据库

mysql_select_db

3,执行SQL查询

mysql_query

4,处理返回的数据

mysql_fetch_array

mysql_num_rows

mysql_fetch_assoc

mysql_fetch_row

etc

*/

class

db_mysql

{

var

$querynum

=

0

//当前页面进程查询数据库的次数

var

$dblink

//数据库连接资源

//链接数据库

function

connect($dbhost,$dbuser,$dbpw,$dbname='',$dbcharset='utf-8',$pconnect=0

,

$halt=true)

{

$func

=

empty($pconnect)

?

'mysql_connect'

:

'mysql_pconnect'

$this->dblink

=

@$func($dbhost,$dbuser,$dbpw)

if

($halt

&&

!$this->dblink)

{

$this->halt("无法链接数据库！")

}

//设置查询字符集

mysql_query("SET

character_set_connection={$dbcharset},character_set_results={$dbcharset},character_set_client=binary",$this->dblink)

//选择数据库

$dbname

&&

@mysql_select_db($dbname,$this->dblink)

}

//选择数据库

function

select_db($dbname)

{

return

mysql_select_db($dbname,$this->dblink)

}

//执行SQL查询

function

query($sql)

{

$this->querynum++

return

mysql_query($sql,$this->dblink)

}

//返回最近一次与连接句柄关联的INSERT，UPDATE

或DELETE

查询所影响的记录行数

function

affected_rows()

{

return

mysql_affected_rows($this->dblink)

}

//取得结果集中行的数目,只对select查询的结果集有效

function

num_rows($result)

{

return

mysql_num_rows($result)

}

//获得单格的查询结果

function

result($result,$row=0)

{

return

mysql_result($result,$row)

}

//取得上一步

INSERT

*** 作产生的

ID,只对表有AUTO_INCREMENT

ID的 *** 作有效

function

insert_id()

{

return

($id

=

mysql_insert_id($this->dblink))

>=

0

?

$id

:

$this->result($this->query("SELECT

last_insert_id()"),

0)

}

//从结果集提取当前行，以数字为key表示的关联数组形式返回

function

fetch_row($result)

{

return

mysql_fetch_row($result)

}

//从结果集提取当前行，以字段名为key表示的关联数组形式返回

function

fetch_assoc($result)

{

return

mysql_fetch_assoc($result)

}

//从结果集提取当前行，以字段名和数字为key表示的关联数组形式返回

function

fetch_array($result)

{

return

mysql_fetch_array($result)

}

//关闭链接

function

close()

{

return

mysql_close($this->dblink)

}

//输出简单的错误html提示信息并终止程序

function

halt($msg)

{

$message

=

"<html>\n<head>\n"

$message

.=

"<meta

content='text/htmlcharset=gb2312'>\n"

$message

.=

"</head>\n"

$message

.=

"<body>\n"

$message

.=

"数据库出错：".htmlspecialchars($msg)."\n"

$message

.=

"</body>\n"

$message

.=

"</html>"

echo

$message

exit

}

}

?>

---