Quickly learn how to use PHP database files_PHP tutorial

PHP is still relatively commonly used, so I studied the PHP database file and shared it with you here. I hope it will be useful to everyone. We will see an application where each table is in a separate database. This is reasonable in very large databases, but for general applications this level of partitioning is not required. Additionally, relational queries cannot be performed across databases, which takes away from the whole idea of ​​using a relational database, not to mention that it would be more difficult to manage tables across multiple databases. So, what should multiple databases look like? First, you need some data. Listing 1 shows such data split into 4 files.

Listing 1. PHP database files

<ol class="dp-xml">
<li class="alt"><span><span>Files.sql:  </span></span></li>
<li class=""><span>CREATE TABLE files (  </span></li>
<li class="alt"><span>id MEDIUMINT,  </span></li>
<li class=""><span>user_id MEDIUMINT,  </span></li>
<li class="alt"><span>name TEXT,  </span></li>
<li class=""><span>path TEXT  </span></li>
<li class="alt"><span>);  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>Load_files.sql:  </span></li>
<li class=""><span>INSERT INTO files VALUES ( 1, 1, 'test1.jpg', 'files/test1.jpg' );  </span></li>
<li class="alt"><span>INSERT INTO files VALUES ( 2, 1, 'test2.jpg', 'files/test2.jpg' );  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>Users.sql:  </span></li>
<li class=""><span>DROP TABLE IF EXISTS users;  </span></li>
<li class="alt"><span>CREATE TABLE users (  </span></li>
<li class=""><span>id MEDIUMINT,  </span></li>
<li class="alt"><span>login TEXT,  </span></li>
<li class=""><span>password TEXT  </span></li>
<li class="alt"><span>);  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>Load_users.sql:  </span></li>
<li class=""><span>INSERT INTO users VALUES ( 1, 'jack', 'pass' );  </span></li>
<li class="alt"><span>INSERT INTO users VALUES ( 2, 'jon', 'pass' );  </span></li>
</ol>

You can create database designs, databases in many ways Access and database-based PHP business logic code that typically ends up with errors, and how to fix them when you encounter them. In the multi-database version of these files, you should load the SQL statements into one database and then load the users SQL statements into another database. The PHP code for querying the database for files associated with a specific user is shown below. The get_user function connects to the database containing the users table and retrieves the ID of a given user. The get_files function connects to the files table and retrieves the file rows associated with a given user. A better way to do all of these things is to load the data into a database and then execute a query, such as the one below.

Listing 2. PHP database file Getfiles.php

<ol class="dp-xml">
<li class="alt"><span><span>＜?php  </span></span></li>
<li class=""><span>require_once("DB.php");  </span></li>
<li class="alt"><span> </span></li>
<li class=""><span>function get_user( $name )  </span></li>
<li class="alt"><span>{  </span></li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">dsn</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">'mysql://root:password@localhost/bad_multi1'</font></span><span>;  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">db</font></span><span> =& DB::Connect( $dsn, array() );  </span>
</li>
<li class=""><span>if (PEAR::isError($db)) { die($db-＞getMessage()); }  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">res</font></span><span> = $db-＞query( "SELECT id FROM users WHERE </span><span class="attribute"><font color="#ff0000">login</font></span><span>=?",array( $name ) );  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">uid</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">null</font></span><span>;  </span>
</li>
<li class="">
<span>while( $res-＞fetchInto( $row ) ) { $</span><span class="attribute"><font color="#ff0000">uid</font></span><span> = $row[0]; }  </span>
</li>
<li class="alt"><span> </span></li>
<li class=""><span>return $uid;  </span></li>
<li class="alt"><span>}  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>function get_files( $name )  </span></li>
<li class=""><span>{  </span></li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">uid</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">get_user</font></span><span>( $name );  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">rows</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">array</font></span><span>();  </span>
</li>
<li class=""><span> </span></li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">dsn</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">'mysql://root:password@localhost/bad_multi2'</font></span><span>;  </span>
</li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">db</font></span><span> =& DB::Connect( $dsn, array() );  </span>
</li>
<li class="alt"><span>if (PEAR::isError($db)) { die($db-＞getMessage()); }  </span></li>
<li class=""><span> </span></li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">res</font></span><span> = $db-＞query( "SELECT * FROM files WHERE </span><span class="attribute"><font color="#ff0000">user_id</font></span><span>=?",array( $uid ) );  </span>
</li>
<li class=""><span>while( $res-＞fetchInto( $row ) ) { $rows[] = $row; }  </span></li>
<li class="alt"><span>return $rows;  </span></li>
<li class=""><span>}  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">files</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">get_files</font></span><span>( 'jack' );  </span>
</li>
<li class="alt"><span> </span></li>
<li class=""><span>var_dump( $files );  </span></li>
<li class="alt"><span>?＞  </span></li>
</ol>

Listing 3. Getfiles_good.php

<ol class="dp-xml">
<li class="alt"><span><span>＜?php  </span></span></li>
<li class=""><span>require_once("DB.php");  </span></li>
<li class="alt"><span> </span></li>
<li class=""><span>function get_files( $name )  </span></li>
<li class="alt"><span>{  </span></li>
<li class="">
<span>$</span><span class="attribute">rows</span><span> = </span><span class="attribute-value">array</span><span>();  </span>
</li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute">dsn</span><span> = </span><span class="attribute-value">'mysql://root:password@localhost/good_multi'</span><span>;  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute">db</span><span> =& DB::Connect( $dsn, array() );  </span>
</li>
<li class=""><span>if (PEAR::isError($db)) { die($db-＞getMessage()); }  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute">res</span><span> = $db-＞query("SELECT files.* FROM users, files WHERE  </span>
</li>
<li class="alt">
<span></span><span class="attribute">users.login</span><span>=? AND </span><span class="attribute">users.id</span><span>=</span><span class="attribute-value">files</span><span>.user_id",  </span>
</li>
<li class=""><span>array( $name ) );  </span></li>
<li class="alt"><span>while( $res-＞fetchInto( $row ) ) { $rows[] = $row; }  </span></li>
<li class=""><span> </span></li>
<li class="alt"><span>return $rows;  </span></li>
<li class=""><span>}  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute">files</span><span> = </span><span class="attribute-value">get_files</span><span>( 'jack' );  </span>
</li>
<li class="alt"><span> </span></li>
<li class=""><span>var_dump( $files );  </span></li>
<li class="alt"><span>?＞  </span></li>
</ol>

The code is not only shorter, but also easier to understand and efficient. Instead of executing two queries, we execute one query. Although this question may sound far-fetched, in practice we usually conclude that all tables should be in the same database unless there is a very compelling reason.

http://www.bkjia.com/PHPjc/446457.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446457.htmlTechArticlePHP is still relatively commonly used, so I studied the PHP database file and shared it with you here. Hope it's useful to everyone. We'll see an application where each...