編輯“WordPress:Displaying Posts Using a Custom Select Query”

== Description ==
== 描述 ==
At some point in your WordPress development career you may be presented with the need to display one or more posts using [[WordPress:Wikipedia:SELECT|SELECT]] criteria not provided by WordPress' [[WordPress:Template Tags/query posts | query_posts]] architecture.  For instance, it may become necessary to [[WordPress:Wikipedia:JOIN|JOIN]] WordPress tables to determine which posts should be displayed, or you may want to use data stored in your own tables to determine which [[WordPress:Writing Posts|posts]] should be displayed.
在你的WordPress發(fā)展歷程的某個時刻，或許你需要通過非WordPress的[[WordPress:Template Tags/query posts | query_posts]] 架構(gòu)提供的[[WordPress:Wikipedia:SELECT|SELECT]]標(biāo)準(zhǔn)來顯示一篇或更多的文章。例如，你有時或許必須[[WordPress:Wikipedia:JOIN|JOIN]] WordPress表格以確定要顯示的文章或使用自己表格中的儲存數(shù)據(jù)來確定要顯示的[[WordPress:Writing Posts|posts]]。

The practical example, outlined below, demonstrates a process of selecting all posts with a particular [[WordPress:Using Custom Fields | Custom Field]] value stored, and displaying them in a [[WordPress:Pages|Page]] based on a [[WordPress:Pages#Creating_your_own_Page_Templates|Page Template]]. Originally, this code was used to implement a post tagging [[WordPress:Plugins|plugin]], which allowed organizing posts in less structured collections than the WordPress [[WordPress:Manage_Categories_SubPanel|Categories]]. Your own usage may be very different, but the content and example should still give you a useful introduction to the general process involved.
以下概述的實(shí)例展示了這樣一個過程：選擇有[[WordPress:Using Custom Fields | Custom Field]]存入值的所有文章并把它們在建立在[[WordPress:Pages#Creating_your_own_Page_Templates|Page Template]]基礎(chǔ)上的[[WordPress:Pages|Page]]顯示出來。這些編碼最初用來執(zhí)行文章標(biāo)簽[[WordPress:Plugins|plugin]]，它允許以比WordPress[[WordPress:Manage_Categories_SubPanel|Categories]]稍無序的構(gòu)架來組織文章。你的使用或許有所不同，但以下的例子仍會給你提供些有用的一般過程說明。

=== Assumptions made in this Article ===
=== 文章假設(shè) ===
Generally, this article assumes you have a working knowledge of [[WordPress:Glossary#PHP|PHP]], [[WordPress:Glossary#MySQL|MySQL]], and WordPress capabilities.
本文通常假設(shè)你擁有[[WordPress:Glossary#PHP|PHP]], [[WordPress:Glossary#MySQL|MySQL]]知識和WordPress 使用能力。

Specific assumptions for the example, however, are:
但此例的特定假設(shè)是：

* You have at least one post with [[WordPress:Using Custom Fields | Custom Fields]] data.  The Custom Fields should have a key of 'tag' and a value of 'email'
*你至少擁有一篇[[WordPress:Using Custom Fields | Custom Fields]]數(shù)據(jù)文章。自定義字段有“標(biāo)簽”鍵和“電子郵件”鍵值。

* You have created a [[WordPress:Pages|Page]] and associated a [[WordPress:Pages#Page_Templates|Page Template]] with that page.  For this example, assume the Template Name is 'Qbased' and was copied from the ''wp-content/themes/index.php'' template.  If you are not familiar with this process, follow the instructions in [[WordPress:Pages#Creating_your_own_Page_Templates|Creating your own Page Templates]].
*你已創(chuàng)建一個[[WordPress:Pages|Page]]并有一個[[WordPress:Pages#Page_Templates|Page Template]]鏈接。在此例中，假定模板名稱為'Qbased'，它是從wp-content/themes/index.php模板復(fù)制的。如果你對此過程不熟悉，按照[[WordPress:Pages#Creating_your_own_Page_Templates|Creating your own Page Templates]]中的說明進(jìn)行操作。

* As this is a somewhat advanced developer topic, familiarity with the core WordPress concept of [[WordPress:The Loop]] is suggested. 
*由于這是稍先進(jìn)的開發(fā)主題，推薦掌握[[WordPress:The Loop]]的WordPress核心概念。

== Code for the Page Template ==
== 網(wǎng)頁模板編碼 ==

===The query===
===查詢===

To begin with, it is necessary to retrieve the [[WordPress:Glossary#Recordset|recordset]] containing the posts you want to display.  To do this, create a result set using the WordPress [[WordPress:Function_Reference/wpdb_Class|$wpdb database class]].  Note that the [[WordPress:Glossary#MySQL|MySQL]] [[WordPress:Wikipedia:SELECT|SELECT]] statement illustrates a '''simple''' [[WordPress:Wikipedia:JOIN|JOIN]].  Here, <tt>$pageposts</tt> will contain an [[WordPress:Glossary#Array|array]] of objects. Each object will represent a '''published''' post that has custom field key-value pair - with the key being 'tag' and the value being 'email':

首先，需要檢索[[WordPress:Glossary#Recordset|recordset]]（數(shù)據(jù)集），里面包含你要顯示的文章。要做到這一點(diǎn)，需要使用WordPress[[WordPress:Function_Reference/wpdb_Class|$wpdb database class]]創(chuàng)建一個result set（結(jié)果集）。注意[[WordPress:Glossary#MySQL|MySQL]] [[WordPress:Wikipedia:SELECT|SELECT]]指令闡明了一個“簡單的” [[WordPress:Wikipedia:JOIN|JOIN]]。<tt>$pageposts</tt>在此會包含[[WordPress:Glossary#Array|array]]對象。每個對象代表一篇有自定義字段key-value（鍵-鍵值）配對且鍵名為tag，值為email的“已發(fā)布”文章。

<pre>
 <?php

 $querystr = "
    SELECT wposts.* 
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
    WHERE wposts.ID = wpostmeta.post_id 
    AND wpostmeta.meta_key = 'tag' 
    AND wpostmeta.meta_value = 'email' 
    AND wposts.post_status = 'publish' 
    AND wposts.post_type = 'post' 
    ORDER BY wposts.post_date DESC
 ";

 $pageposts = $wpdb->get_results($querystr, OBJECT);
 
 ?>
</pre>
<pre>
 <?php

 $querystr = "
    SELECT wposts.* 
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
    WHERE wposts.ID = wpostmeta.post_id 
    AND wpostmeta.meta_key = 'tag' 
    AND wpostmeta.meta_value = 'email' 
    AND wposts.post_status = 'publish' 
    AND wposts.post_type = 'post' 
    ORDER BY wposts.post_date DESC
 ";

 $pageposts = $wpdb->get_results($querystr, OBJECT);
 
 ?>
</pre>


===The Revised Loop===
===已修改的Loop（循環(huán)）===

Now, to display posts collected into <tt>$pageposts</tt> by the previous [[WordPress:Wikipedia:SELECT|SELECT]] criteria, you need to replace [[WordPress:The Loop]] with your own loop code in the ''Qbased'' Page Template.  This requires creating a revised loop that cycles through the posts stored in <tt>$pageposts</tt> and displays them. Note: the structure / markup in the loop below is taken from the WordPress '''default''' [[WordPress:Using Themes|theme]].

現(xiàn)在，若要通過以前的[[WordPress:Wikipedia:SELECT|SELECT]] 標(biāo)準(zhǔn)來顯示<tt>$pageposts</tt>中的文章，你需要用Qbased網(wǎng)頁模板中你自己的循環(huán)編碼來替代[[WordPress:The Loop]]。這需要創(chuàng)建一個已修改的循環(huán)（loop），使它能夠循環(huán)<tt>$pageposts</tt>中的文章并顯示它們。注意：下面loop(循環(huán))中的結(jié)構(gòu)/標(biāo)記取自WordPress“默認(rèn)”[[WordPress:Using Themes|theme]].
。

<pre>
 <?php if ($pageposts): ?>
 <?php foreach ($pageposts as $post): ?>
 <?php setup_postdata($post); ?>
 
 <div class="post" id="post-<?php the_ID(); ?>">
 <h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>">
    <?php the_title(); ?></a></h2>
    <small><?php the_time('F jS, Y') ?> <!-- by <?php the_author() ?> --></small>
    <div class="entry">
       <?php the_content('Read the rest of this entry &raquo;'); ?>
    </div>
    <p class="postmetadata">Posted in <?php the_category(', ') ?> | <?php edit_post_link('Edit', '', ' | '); ?>  
    <?php comments_popup_link('No Comments &#187;', '1 Comment &#187;', '% Comments &#187;'); ?></p>
 </div>
 <?php endforeach; ?>
 <?php else : ?>
    <h2 class="center">Not Found</h2>
    <p class="center">Sorry, but you are looking for something that isn't here.</p>
    <?php include (TEMPLATEPATH . "/searchform.php"); ?>
 <?php endif; ?>
</pre>
<pre>
 <?php if ($pageposts): ?>
 <?php foreach ($pageposts as $post): ?>
 <?php setup_postdata($post); ?>
 
 <div class="post" id="post-<?php the_ID(); ?>">
 <h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>">
    <?php the_title(); ?></a></h2>
    <small><?php the_time('F jS, Y') ?> <!-- by <?php the_author() ?> --></small>
    <div class="entry">
       <?php the_content('Read the rest of this entry &raquo;'); ?>
    </div>
    <p class="postmetadata">Posted in <?php the_category(', ') ?> | <?php edit_post_link('Edit', '', ' | '); ?>  
    <?php comments_popup_link('No Comments &#187;', '1 Comment &#187;', '% Comments &#187;'); ?></p>
 </div>
 <?php endforeach; ?>
 <?php else : ?>
    <h2 class="center">Not Found</h2>
    <p class="center">Sorry, but you are looking for something that isn't here.</p>
    <?php include (TEMPLATEPATH . "/searchform.php"); ?>
 <?php endif; ?>
</pre>


And that's it!
就是它！

To go through the important parts of the code, line by line, you have:

一行一行地審查編碼的重要部分，你必須：

* A test to make sure that the query that populated <tt>$pageposts</tt> actually found some posts that matched the [[WordPress:Wikipedia:SELECT|SELECT]] criteria:
*測試以確保<tt>$pageposts</tt>中的查詢可以查到符合[[WordPress:Wikipedia:SELECT|SELECT]]標(biāo)準(zhǔn)中的文章：

<pre>
<?php if ($pageposts): ?>
</pre>
* A [[WordPress:Wikipedia:Foreach|foreach loop]] to go through the posts returned in <tt>$pageposts</tt> and display them:
<pre>
<?php foreach($pageposts as $post): ?>
</pre>
<pre>
<?php if ($pageposts): ?>
</pre>
* A [[WordPress:Wikipedia:Foreach|foreach loop]] to go through the posts returned in <tt>$pageposts</tt> and display them:
*[[WordPress:Wikipedia:Foreach|foreach loop]]審查已返回<tt>$pageposts</tt>的文章，并顯示文章：
<pre>
<?php foreach($pageposts as $post): ?>
</pre>


* And, a call to the WordPress post formatting function, <tt>setup_postdata()</tt>, that automatically populates the required variables: 
<pre>
<?php setup_postdata($post); ?>
</pre>
*調(diào)用WordPress文章格式化函數(shù)，<tt>setup_postdata()</tt>,自動填入所需變量：
<pre>
<?php setup_postdata($post); ?>
</pre>
 	

==== Within the Loop ====
==== Loop （循環(huán)）內(nèi)部====


Because <tt>setup_postdata($post);</tt> was called in our example, you can use the same [[WordPress:Template Tags | template tags]] that can be included in a normal WordPress post loop, like <tt>the_content()</tt> and <tt>the_permalink()</tt>. This means that you can create your own post display results using a Page Template with a minimum amount of fuss, automatically taking advantage of the various plugins you may have activated in your WordPress blog to provide extra formatting and functionality.
由于例子中調(diào)用了<tt>setup_postdata($post);</tt>，你可以使用可包括在正常Wordpress循環(huán)（loop）中的相同[[WordPress:Template Tags | template tags]]，如<tt>the_content()</tt> 和 <tt>the_permalink()</tt>。這意味著你能夠較方便地用網(wǎng)頁模板創(chuàng)建自己的文章顯示結(jié)果，并自動利用你的Wordpress博客已激活的各種插件提供額外的格式和功能。

=== The Completed Page Template ===
===已完成的網(wǎng)頁模板===


Here is a complete example of the new template that works with the WordPress '''default''' theme.
這是Wordpress“默認(rèn)”主題運(yùn)行的新模板的完整事例。

<pre>
<?php
/*
Template Name: Qbased
*/
?>

<?php get_header(); ?>

<div id="content" class="narrowcolumn">

<?php

 $querystr = "
    SELECT wposts.* 
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
    WHERE wposts.ID = wpostmeta.post_id 
    AND wpostmeta.meta_key = 'tag' 
    AND wpostmeta.meta_value = 'email' 
    AND wposts.post_status = 'publish' 
    AND wposts.post_type = 'post' 
    AND wposts.post_date < NOW() 
    ORDER BY wposts.post_date DESC
 ";

 $pageposts = $wpdb->get_results($querystr, OBJECT);

?>
 <?php if ($pageposts): ?>
  <?php foreach ($pageposts as $post): ?>
    <?php setup_postdata($post); ?>

    <div class="post" id="post-<?php the_ID(); ?>">
      <h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>">
      <?php the_title(); ?></a></h2>
      <small><?php the_time('F jS, Y') ?> <!-- by <?php the_author() ?> --></small>
      <div class="entry">
         <?php the_content('Read the rest of this entry ?'); ?>
      </div>
  
      <p class="postmetadata">Posted in <?php the_category(', ') ?> | <?php edit_post_link('Edit', '', ' | '); ?>  
      <?php comments_popup_link('No Comments ?', '1 Comment ?', '% Comments ?'); ?></p>
    </div>
  <?php endforeach; ?>
  
  <?php else : ?>
    <h2 class="center">Not Found</h2>
    <p class="center">Sorry, but you are looking for something that isn't here.</p>
    <?php include (TEMPLATEPATH . "/searchform.php"); ?>
 <?php endif; ?>

</div>

<?php get_sidebar(); ?>

<?php get_footer(); ?>
</pre>

<pre>
<?php
/*
Template Name: Qbased
*/
?>

<?php get_header(); ?>

<div id="content" class="narrowcolumn">

<?php

 $querystr = "
    SELECT wposts.* 
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
    WHERE wposts.ID = wpostmeta.post_id 
    AND wpostmeta.meta_key = 'tag' 
    AND wpostmeta.meta_value = 'email' 
    AND wposts.post_status = 'publish' 
    AND wposts.post_type = 'post' 
    AND wposts.post_date < NOW() 
    ORDER BY wposts.post_date DESC
 ";

 $pageposts = $wpdb->get_results($querystr, OBJECT);

?>
 <?php if ($pageposts): ?>
  <?php foreach ($pageposts as $post): ?>
    <?php setup_postdata($post); ?>

    <div class="post" id="post-<?php the_ID(); ?>">
      <h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>">
      <?php the_title(); ?></a></h2>
      <small><?php the_time('F jS, Y') ?> <!-- by <?php the_author() ?> --></small>
      <div class="entry">
         <?php the_content('Read the rest of this entry ?'); ?>
      </div>
  
      <p class="postmetadata">Posted in <?php the_category(', ') ?> | <?php edit_post_link('Edit', '', ' | '); ?>  
      <?php comments_popup_link('No Comments ?', '1 Comment ?', '% Comments ?'); ?></p>
    </div>
  <?php endforeach; ?>
  
  <?php else : ?>
    <h2 class="center">Not Found</h2>
    <p class="center">Sorry, but you are looking for something that isn't here.</p>
    <?php include (TEMPLATEPATH . "/searchform.php"); ?>
 <?php endif; ?>

</div>

<?php get_sidebar(); ?>

<?php get_footer(); ?>
</pre>

It is important to note here that the above example will work '''only''' when OBJECT is passed as the "output_type" parameter for <code>$wpdb->get_results()</code>. setup_postdata() does not seem to work when ARRAY_A or ARRAY_N is passed in $wpdb->get_results().
這里值得注意的是，上述例子“只有”當(dāng)<code>$wpdb->get_results()</code>是以"output_type"為參數(shù)，面向?qū)ο笸ㄟ^時才運(yùn)行。當(dāng)ARRAY_A 或ARRAY_N在$wpdb->get_results()通過時，setup_postdata()似乎不運(yùn)行。


==Query based on Custom Field and Category==

==自定義字段和類別基礎(chǔ)上的查詢==

This next example sets the $querystr variable used in the above example, to get all posts in Categories 1,2, and 3, that have the meta_key 'paragraf', and then sorted ascending by the meta_values.  This example gleaned from Otto42's response in [http://wordpress.org/support/topic/121011 Forum Topic 121011].
此事例設(shè)置了上個事例中使用的$querystr變量以獲得類別1，2，和3中的有meta_key 'paragraf'的所有文章，并按meta_values升序排列。此例來源于Otto42在[http://wordpress.org/support/topic/121011 Forum Topic 121011].
中的回復(fù)。

<pre>
 $querystr = "
    SELECT $wpdb->posts.*
    FROM $wpdb->posts
    LEFT JOIN $wpdb->postmeta ON ($wpdb->posts.ID = $wpdb->postmeta.post_id)
    LEFT JOIN $wpdb->post2cat ON ($wpdb->posts.ID = $wpdb->post2cat.post_id)
    WHERE $wpdb->postmeta.meta_key = 'paragraf'
    AND $wpdb->posts.post_status = 'publish'
    AND $wpdb->posts.post_type = 'post'
    AND $wpdb->post2cat.category_id IN (1,2,3)
    ORDER BY $wpdb->postmeta.meta_value ASC
    ";

</pre>

<pre>
 $querystr = "
    SELECT $wpdb->posts.*
    FROM $wpdb->posts
    LEFT JOIN $wpdb->postmeta ON ($wpdb->posts.ID = $wpdb->postmeta.post_id)
    LEFT JOIN $wpdb->post2cat ON ($wpdb->posts.ID = $wpdb->post2cat.post_id)
    WHERE $wpdb->postmeta.meta_key = 'paragraf'
    AND $wpdb->posts.post_status = 'publish'
    AND $wpdb->posts.post_type = 'post'
    AND $wpdb->post2cat.category_id IN (1,2,3)
    ORDER BY $wpdb->postmeta.meta_value ASC
    ";

</pre>


'''with wordpress 2.3 you need to update the sql query shown above to this:'''
This example gleaned from kernow's response in [http://wordpress.org/support/topic/121011 Forum Topic 121011]

'''使用 wordpress2.3，你需要把以上顯示的sql查詢更新為：'''
此例來源于kernow在[http://wordpress.org/support/topic/121011 Forum Topic 121011] 中的回復(fù)

<pre>
SELECT * FROM $wpdb->posts
LEFT JOIN $wpdb->postmeta ON($wpdb->posts.ID = $wpdb->postmeta.post_id)
LEFT JOIN $wpdb->term_relationships ON($wpdb->posts.ID = $wpdb->term_relationships.object_id)
LEFT JOIN $wpdb->term_taxonomy ON($wpdb->term_relationships.term_taxonomy_id = $wpdb->term_taxonomy.term_taxonomy_id)
WHERE $wpdb->term_taxonomy.term_id = 1,2,3
AND $wpdb->term_taxonomy.taxonomy = 'category'
AND $wpdb->posts.post_status = 'publish'
AND $wpdb->postmeta.meta_key = 'paragraf'
ORDER BY $wpdb->postmeta.meta_value ASC
</pre>
<pre>
SELECT * FROM $wpdb->posts
LEFT JOIN $wpdb->postmeta ON($wpdb->posts.ID = $wpdb->postmeta.post_id)
LEFT JOIN $wpdb->term_relationships ON($wpdb->posts.ID = $wpdb->term_relationships.object_id)
LEFT JOIN $wpdb->term_taxonomy ON($wpdb->term_relationships.term_taxonomy_id = $wpdb->term_taxonomy.term_taxonomy_id)
WHERE $wpdb->term_taxonomy.term_id = 1,2,3
AND $wpdb->term_taxonomy.taxonomy = 'category'
AND $wpdb->posts.post_status = 'publish'
AND $wpdb->postmeta.meta_key = 'paragraf'
ORDER BY $wpdb->postmeta.meta_value ASC
</pre>

== Acknowledgements ==
==致謝 ==

Many thanks to [http://wordpress.org/support/profile/6445 Kafkaesquii] for pointing out a simpler method of populating the appropriate global variables, etc, using setup_postdata().
非常感謝[http://wordpress.org/support/profile/6445 Kafkaesquii]指出填寫適當(dāng)全局變量等的更簡便方法：使用setup_postdata()。