Detailed explanation of operating MySQL database with PHP (1)

1. PHP connects to MySQL server

mysql_connect()

Basic syntax

• Description: PHP connects to MySQL server

• Syntax: resource $link = mysql_connect($hostname, $username, $password)

• Parameters:
  

• $hostname: It is the domain name or IP address of the MySQL server, and you can also add the port number (3306). For example: localhost:3306

• #$username: is the username of the MySQL server. For example: root

• #$password: is the user password of the MySQL server.

• Return value: If the execution is successful, a resource identifier is returned. If the execution fails, return FALSE If the

@

characters are not added, a system error will be reported. You can see the error message below, which contains a lot of user information. Security is not good. Use the @

character to block this system error and improve security.

<?php

ini_set(display_errors, 1); //设置错误为：显示

//0.数据库配置信息
$db_host = &#39;loca1lhost&#39;;
$db_user = &#39;root&#39;;
$db_pwd = &#39;yeoman&#39;;

//1.PHP连接MySQL服务器
$link = @mysql_connect($db_host, $db_user, $db_pwd); //@用于屏蔽系统错误

//如果连接失败，则输出错误信息，并中止程序运行
if(!$link){
    echo "PHP连接MySQL失败！".mysql_error();
    exit(); //中止程序继续向下运行
}

?>

Otherfunctionsand symbols

##exit()

Description: Output a prompt message and stop the script from continuing to run.

Syntax: void exit([$msg])

Parameters: $msg is optional. If omitted, only the script is aborted.

• Example: exit("PHP connection error")
##mysql_error()

• Description: Returns the text error message when the last MySQL execution failed.

Syntax: mysql_error()

##Shielding system errors@

• Description:
  @

Can shield various function call errors, or

include file errors, but cannot be used in function definitions or class definitions Before.

• 2. Select MySQL database

  mysql_select_db

  ()

Syntax

Description: Select the database currently to be operated

Syntax: bool mysql_select_db ( string $database_name [, resource $link ] )

Parameters:

• $database_name: Specify the name of the database to be selected.

• $link: Optional. Specifies the currently active connection. If omitted, the
• last

  
  open active connection will be used.

• Return value: If the database selection is successful,

TRUE

• will be returned. If database selection fails, FALSE is returned.

• Operation

  Warning: mysql_connect() [<a href=&#39;function.mysql-connect&#39;>function.mysql-connect</a>]: 
  Unknown MySQL server host &#39;local1host&#39; (0) in /Applications/MAMP/htdocs/php_test/php_mysql.php on line 17

  3. Set the data character set returned by MySQL

Send a request to the MySQL server or return the data of the request result Character set

.

<?php

//0.数据库配置信息
$db_name = &#39;yeoman92&#39;;

//2.选择当前数据库
if(!mysql_select_db($db_name, $link)){
    echo "选择数据库{$db_name}失败！".mysql_error();
    exit();
}

?>

4. Execute the MySQL statement

##mysql_query()

Syntax

Description: Send a MySQL query.

Syntax: resource mysql_query (string $query [, resource $link])Parameters:

• Add records: $query = "INSERT INTO news(title,content) VALUES('title', 'content')"

• Delete records: $query = “DELETE FROM news WHERE id=10”

• Modify record: $query = “UPDATE news SET title = ‘New title’, content = ‘New content’ WHERE id= 80"
  

Query record: $query = "SELECT * FROM news WHERE id

• $query：指要发送的SQL语句。
  

• $link：可选项。指上一次打开的活动连接。

• 返回值：
  

• 结果集也是一个资源标识符，是到MySQL数据的一个引用地址。

• 如果执行SELECT、SHOW、DESCRIBE命令，成功时返回结果集，失败时返回FALSE。
  

• 如果执行其它的SQL语句，执行成功返回TRUE，执行失败返回FALSE。

• 举例：
  

• $result = mysql_query(“SELECT * FROM news WHERE id

• $result = mysql_query(“DELETE * FROM news WHERE id=100”)

操作

//4.执行SQL查询：向MySQL服务器发出查询的请求$
sql = &#39;SELECT * FROM 007_news WHERE id<100&#39;;
$result = mysql_query($sql, $link);

5. 从结果集中取出一行数据

1. mysql_fetch_row()

语法

• 描述：从结果集中取得一行作为枚举数组。

• 语法：array mysql_fetch_row ( resource $result )

• 参数：$result是结果集变量。

• 返回值：返回一个枚举数组，也就是从0开始的正整数下标。这里的下标，是与表的字段下标是对应的。

• 举例：$arr = mysql_fetch_row($result)

操作

//5.取出一条记录作为枚举数组返回
$arr = mysql_fetch_row($result);echo "<pre class="brush:php;toolbar:false">";
print_r($arr);echo "

";

执行结果

Array(
    [0] => 17
    [1] => 1
    [2] => cctv中学生信息化教学实验基地共建工程在京启动
    [3] => admin
    [4] => 中小学课外辅导网
    [5] => 
    [6] => 
    [7] => 50
    [8] => 
    [9] => 52
    [10] => 1339340691)

2. mysql_fetch_array()

• 描述：从结果集中取出一行，作为混合数组返回。

• 语法：array mysql_fetch_array ( resource $result [, int $result_type ] )

• 参数：
  

• MYSQL_BOTH：默认的。也就是两种下标都存在。

• MYSQL_ASSOC：只有字符下标的数组。相当于mysql_fetch_assoc()的功能。

• MYSQL_NUM：只有整数下标的数组。相当于mysql_fetch_row()的功能。

• 以上三个参数是常量，系统常量必须全大写。

• $result：是指结果集变量。

• $result_type：是指返回的数组的类型。取值：MYSQL_BOTH、MYSQL_ASSOC、MYSQL_NUM
  

• 返回值：返回一个数组，至于是什么数组，取决于第二个参数。

• 举例：
  

• $arr = mysql_fetch_array($result) //混合数组

• $arr = mysql_fetch_array($result , MYSQL_ASSOC ) //关联数组

• $arr = mysql_fetch_array($result , MYSQL_NUM) //枚举数组

3. mysql_fetch_assoc()

• 描述：从结果集中取一行，以关联数组返回。

• 语法：array mysql_fetch_assoc(resource $result)

• 举例：$arr = mysql_fetch_assoc($result)

附：完整PHP代码

<?php

ini_set(display_errors, 1); //设置错误为：显示

//0.数据库配置信息
$db_host = &#39;localhost&#39;;
$db_user = &#39;root&#39;;
$db_pwd = &#39;yeoman&#39;;
$db_name = &#39;yeoman92&#39;;

//1.PHP连接MySQL服务器
$link = @mysql_connect($db_host, $db_user, $db_pwd); //@用于屏蔽系统错误

//如果连接失败，则输出错误信息，并中止程序运行
if(!$link){
    echo "PHP连接MySQL失败！".mysql_error();
    exit(); //中止程序继续向下运行
}

//2.选择当前数据库
if(!mysql_select_db($db_name, $link)){
    echo "选择数据库{$db_name}失败！".mysql_error();
    exit();
}

//3.设置MySQL返回的数据字符集
mysql_query("set names utf8");

//4.执行SQL查询：向MySQL服务器发出查询的请求
$sql = &#39;SELECT * FROM 007_news WHERE id<100&#39;;
$result = mysql_query($sql, $link);

//5.取出一条记录作为枚举数组返回
$arr = mysql_fetch_row($result);
echo "<pre class="brush:php;toolbar:false">";
print_r($arr);
echo "

"; ?>

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