来自数据库的分组结果

Question

我正在尝试显示基于id的类别结果，我从数据库中获取信息，但它再次创建了一个类别标题。

例如：

标题类别演示cat 1 专题1“禁止酷刑公约”第1条 标题类别演示cat 1 专题2“禁止酷刑公约”第1条 标题类别演示cat 2 专题3“禁止酷刑公约”第二届会议

当它应该显示：

标题类别演示cat 1 专题1“禁止酷刑公约”第1条 专题2“禁止酷刑公约”第1条 标题类别演示cat 2 专题3“禁止酷刑公约”第二届会议

<table class="table table-bordered table-hover">
    <?php

$sql = "SELECT * FROM forums, forum_categories WHERE forum_categories.cat_id = forums.cat_id ORDER BY forum_categories.cat_id";
$result = query($sql);

while (($row = mysqli_fetch_assoc($result)) != false) {
         
    $cat_id = $row['cat_id'];    
    $cat_title = $row['cat_title'];
    
    echo "<thead>";
             echo "<tr>";
                 echo "<th colspan='4'>$cat_title</th>";
            "</tr>";
         echo "</thead>";
         echo "<tbody>";
                      
  
    $forums_cat_id = $row['cat_id'];
    $forum_name = $row['forum_name']; 
    $forum_desc = $row['forum_desc'];
    $forum_last_post_id = $row['forum_last_post_id'];
    
    echo "<tr>";
    
    echo "<td>$forums_cat_id</td>";
    echo "<td>$forum_name<br>$forum_desc<br>Admin</td>";
    echo "<td>0</td>";
    echo "<td>0</td>";  
    echo "</tr>";
}

?>   
    </tbody>
</table>

Answer 1

您正在打印每个结果的标题，MySQL为每一行返回。因此，无论何时发现“新”类别，您都不会做出区分。通过创建一个像数组一样的临时变量，可以很简单地做到这一点。例如：

$displayedCategories = array();

while (($row = mysqli_fetch_assoc($result)) != false) {
    if (!in_array($row['cat_id'], $displayedCategories)) {
        // This is a new category, display it and save it in $displayedCategories
        $displayedCategories[] = $row['cat_id'];
        echo "<thead>";
        echo "<tr>";
        echo "<th colspan='4'>$cat_title</th>";
        echo "</tr>";
        echo "</thead>";
    }

    // Do the other stuff here...
}

这样，任何未遇到的“新”类别都会被打印一次，并将类别id保存到$displayedCategories数组中。如果再次遇到相同的类别，则不会再次输出标头。

Answer 2

<table class="table table-bordered table-hover"><tbody>
    <?php

    $sql = "SELECT * FROM forums, forum_categories WHERE forum_categories.cat_id = forums.cat_id ORDER BY forum_categories.cat_id";
    $result = query($sql);
    $cur_cat = '';
    while (($row = mysqli_fetch_assoc($result)) != false) {

        $cat_id = $row['cat_id'];    
        $cat_title = $row['cat_title'];

        if($cat_title != $cur_cat) {
            echo "<thead>";
                 echo "<tr>";
                     echo "<th colspan='4'>$cat_title</th>";
                "</tr>";
            echo "</thead>";
            $cur_cat = $cat_title;
         }


        $forums_cat_id = $row['cat_id'];
        $forum_name = $row['forum_name']; 
        $forum_desc = $row['forum_desc'];
        $forum_last_post_id = $row['forum_last_post_id'];

        echo "<tr>";

        echo "<td>$forums_cat_id</td>";
        echo "<td>$forum_name<br>$forum_desc<br>Admin</td>";
        echo "<td>0</td>";
        echo "<td>0</td>";  
        echo "</tr>";
    }

    ?>
</tbody></table>