从CodeIgniter（或任何MVC平台）中的数据库中提取数据？

Question

我有这样的型号：

public function index_loop() { 
     $post_user = $this->db->query("SELECT posts.post_title, posts.post_content, posts.post_date, users.username FROM posts LEFT JOIN users ON posts.user_id = users.user_id ORDER BY posts.post_ID DESC"); 
     //$categories = $this->db->query("SELECT categories.cat_name, categories.cat_id FROM 
     //$comments = $this->db->query("SELECT COUNT(comment_id) FROM comments WHERE 
     return $post_user->result_array(); 
    } 

我需要的是要为每个帖子和评论类（虽然我想，如果我弄清楚路过不是注释类别是相同的方式）

中查看文件：

<?php foreach($posts as $zz) { ?> 
     <div class="article"> 
      <h2><?php echo $zz['post_title']; ?></h2> 
      <p>Posted by <a href=""><?php echo $zz['username']; ?></a> | Filed under <a href="#">templates</a>, <a href=>internet</a></p> 
      <p><?php echo $zz['post_content']; ?></p> 
      <p><a href=>Read more</a> | <a href=>Comments (5)</a> | <?php echo $zz['post_date']; ?></p> 
     </div> <?php } ?> 

所以，如果我想在每个博客圈类别我需要博客ID，我怎么得到它，如果我做的型号所有查询？ 同样的评论

是不是很好，我做了一个大型复杂的数据库查询（这是很难但我能做到）或者我可以做2或3个单独的较小的查询？

Answer 1

Codeigniter允许您将数据库结果作为对象（例如模型对象）返回，这使得数据更易于使用。您可以将初始查询发送到Posts表，将posts.id字段包含在结果集中，并将Post_model类的名称传递给$db->query->result()函数，以告知代码单元您希望将结果作为实例返回Post_model类。

然后，您可以通过post_id定义对Post_model类GetCategories由post_id和GetComments方法，然后调用这些方法来填充你的$categories和$comments收藏从您的查询返回的每一Post_model。

下面是一个例子，我希望它能帮助：

<?php foreach($posts as $zz) { ?> 
     <div class="article"> 
      <h2><?php echo $zz->post_title; ?></h2> 
      <p>Posted by <a href=""><?php echo $zz->username; ?></a> | 

       Filed under 
       <?php foreach($zz->categories as $category) { 
         echo '<a href="#">{$category->name}</a>, '; 
        } 
       ?> 
      </p> 
      <p><?php echo $zz->post_content; ?></p> 
      <p><a href=>Read more</a> | <a href=>Comments (5)</a> | <?php echo $zz->post_date; ?></p> 
     </div> <?php } ?> 

至于：

public class Post_model extends CI_Model 
    { 

     // All the properties in the Posts table, as well as a couple variables to hold the categories and comments for this Post: 
     public $id; 
     public $post_title; 
     public $post_content; 
     public $post_date; 
     public $username;   
     public $categories; 
     public $comments; 

     public function index_loop() 
     { 
       return $this->GetAllPosts(); 
     } 

     // function to get all posts from the database, including comments and categories. 
     // returns an array of Post_model objects 
     public function GetAllPosts() 
     { 
       // define an empty array to hold the results of you query. 
       $all_posts = array(); 

       // define your sql query. NOTE the POSTS.ID field has been added to the field list 
       $sql = "SELECT posts.id, 
           posts.post_title, 
           posts.post_content, 
           posts.post_date, 
           users.username 
         FROM posts LEFT JOIN users ON posts.user_id = users.user_id 
         ORDER BY posts.post_id DESC"; 

       // issue the query 
       $query = $this->db->query($sql); 

       // loop through the query results, passing a string to result() which represents a class to instantiate 
       //for each result object (note: this class must be loaded) 

       foreach($query->result("Post_model") as $post) 
       { 
         $post->categories = $this->GetPostCategories($post->id); 
         $post->comments = $this->GetPostComments($post->id); 
         $all_posts[] = $post; 
       } 

       return $all_posts; 
     } 

     // function to return categories for a given post_id. 
     // returns an array of Category_model objects. 
     public function GetPostCategories($post_id) 
     { 
       $sql = "SELECT category.id, ... WHERE post_id = ?"; 
       $query = $this->db->query($sql, array($post_id)); 
       $categories = array(); 
       foreach($query->result("Category_model") as $category) 
       { 
         $categories[] = $category; 
       } 
       return $categories; 
     } 

     // function to return comments for a given post_id. 
     //returns an array of Comment_model objects 
     public function GetPostComments($post_id) 
     { 
       $sql = "SELECT comment.id, ... WHERE post_id = ?"; 
       $query = $this->db->query($sql, array($post_id)); 
       $comments = array(); 
       foreach($query->result("Comment_model") as $comment) 
       { 
         $comments[] = $comment; 
       } 
       return $comments; 
     }  
} 

然后，在你看来，你可以为Post_model对象，而不是作为result_arrays访问$帖子阵列效率问题，它将取决于很多因素（数据库与Web服务器位于同一台计算机上，有多少帖子等等）。单个大型查询通常会比几个小型查询执行得更快，但需要通过分析来真正确定性能增益是否值得寻求。我总是倾向于尝试编写可读/可理解的代码，而不是以增加复杂性为代价进行优化。

Answer 2

你可以做1件事。

作出不同的分类表和评论表。

category_id将与post_table中的category_id列相链接。

在评论表中，创建将与post_id中的post_id链接在一起的列post_id。

然后您可以通过此扩展查询一次检索所有信息。

$post_user = $this->db->query("SELECT posts.post_title, posts.post_content, posts.post_date, users.username FROM posts LEFT JOIN users ON posts.user_id = users.user_id LEFT JOIN category ON category.category_id = post.category_id ORDER BY posts.post_ID DESC"); 

在这里你得到了类别。

对于评论，我不知道你想如何输出。 Yan说，一种方法是。如果你可以更具体，我可以建议一些更简单的方法。