php - 我怎样才能使这个简单的 block 更短更好？

Question

我正在使用以下未经深思熟虑的代码块来检索类别及其主题。

$query1 = "SELECT * from categories";

$result = mysql_query($query1);

while ($out = mysql_fetch_assoc($result)){
    //category
    print '<h2>' . $out['name'] . '</h2>';

    $query2 = "SELECT * from topics where fkid = $out[id]";    
    $result2 = mysql_query($query2);

    while($top = mysql_fetch_assoc($result2)){
        //topic
        print $top['name'] . '<br>';
    }

}

上面的技巧。我知道这不是最实用的，这就是我问这个小组的原因。

我怎样才能改进它，让它更实用、更简单？

Answer 1

JOIN 的经典案例:

SELECT * FROM categories JOIN topics ON categories.id = topic.fkid ORDER BY categories.name;

然后要打印，我们只打印标题是否已更改(感谢 Rajasur!):

$catname = "";
while ($out = mysql_fetch_assoc($result))
{
  if ($out["name"] != $catname) // maybe need strcmp here
  {
    $catname = $out["name"];
    print($catname)
  }
  /* print the rest */
}