MYSQL：选择按字母顺序排序的父级和按字母顺序排序的子级

Question

我制作了一个简单的表格来了解父子关系，但我似乎没有得到正确的结果。我要排序

1. 按“姓名”字段的字母顺序排列，仅限没有父母的人 (parent_id==0)
2. 但是，只要有父级的子行，它们应该打印在父级之后，也按名称的字母顺序排序。

示例表：

================================================ ==============

CREATE TABLE IF NOT EXISTS `test` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `parent_id` int(11) NOT NULL DEFAULT '0',
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=9 ;

--
-- Dumping data for table `test`
--

INSERT INTO `test` (`id`, `parent_id`, `name`) VALUES
(1, 4, 'Zorg'),
(2, 0, 'Woordolack'),
(3, 4, 'Akriller'),
(4, 0, 'Metabrusher'),
(5, 2, 'Intersplitter'),
(6, 0, 'Beaverbrain'),
(7, 4, 'Torgeoruos'),
(8, 2, 'Deptezaurus');

================================================ ==============

这是我想使用 PHP 输出到 Web 浏览器的内容：

 Beaverbrain
 Metabrusher
 -> Akriller
 -> Torgeoruos
 -> Zorg
 Woordolack
 -> Deptezaurus
 -> Intersplitter

================================================ ==============

我应该说这是一个示例表，只是为了展示这个想法，因此可以通过任何方式对其进行修改以获得正确的结果。

Answer 1

你可以试试这个查询

SELECT IF(child = '',parent,CONCAT('->',child)) as value 
FROM
    (SELECT parent.name as parent,child.name as child
     FROM test parent 
       INNER JOIN 
       (SELECT id,parent_id,name FROM test 
        UNION 
        SELECT null,id,'' FROM test
        WHERE parent_id = 0)child
     WHERE parent.parent_id = 0
     AND child.parent_id = parent.id
     ORDER BY parent,child
     )parent_child

sqlFiddle

查询所做的是 INNER JOIN 测试与 test 并找出哪些是父母和孩子。内部 UNION SELECT null,id,'' FROM test WHERE parent_id = 0 创建一个空的 child(ren) 用于显示目的。然后外部 SELECT 看看孩子是否是 '' 它打印出父母，否则它在孩子前面连接 ->。这样你就可以得到你想要的结果。

以下版本可能会快一点。因为我们将只创建具有 NULL 子项的父项，而不是使用子项作为 INNER JOIN 的一部分（上图）。

SELECT IF(child IS NULL,parent,CONCAT('->',child)) as value 
FROM
 (SELECT parent.name as parent,child.name as child
    FROM test parent 
   INNER JOIN test child ON child.parent_id = parent.id
   WHERE parent.parent_id = 0
  UNION
  SELECT test.name as parent,NULL as child    #This creates a NULL child row
    FROM test WHERE test.parent_id = 0        #for parent display purpose
  ORDER BY parent,child
 )parent_child

sqlFiddle

不过，我会改用下面的查询，并在 PHP 中检查 isParent 标志是 1 还是 0，然后显示相应的字段。

SELECT 0 as isParent,parent.name as parent,child.name as child,
       parent.id as parentId,child.id as childId
  FROM test parent 
 INNER JOIN test child ON child.parent_id = parent.id
 WHERE parent.parent_id = 0
UNION
SELECT 1 as isParent,test.name as parent,NULL as child,
       test.id as parentId,NULL as childId
  FROM test WHERE test.parent_id = 0       
ORDER BY parent,child

sqlFiddle

Answer 2

试试这个解决方案：

SELECT
    A.id,
    A.name
FROM 
    `test` AS A LEFT JOIN `test` AS B ON A.`parent_id` = B.`id`
GROUP BY
    A.`id`
ORDER BY
    IFNULL(B.`name`, A.`name`), 
    COALESCE(A.`parent_id`, A.`id`), 
    A.`parent_id` != 0, 
    A.`name`;

Answer 3

在 PHP 中使用几个简单的查询，

    $r1 = $db->query("select * from test where parent_id = 0 order by name asc") or die('err in q1');
    while($arr1 = $r1->fetch_assoc()){
            $parent = $arr1['name'];
            $parent_id = $arr1['id'];
            echo $parent
            $r2 = $db->query("select * from test where parent_id = $parent order by name asc") or die('err in q2');
            while($arr2 = $r2->fetch_assoc()){
                 $child = $arr2['name'];
                 echo $child."<br />";
            }
    }

Answer 4

在管理分层数据时，您可以改用简单的 PHP 递归函数，

 function DisplayTree( $parent , $depth)     {                                                                                                    
    $sql = $this->db->query("SELECT id,name FROM '$table' WHERE parent_id = '$parent'");

      foreach($sql->result() as $field ) {  
        print "<fieldset style=\"margin-left:$depth%; width:300px\">";  
            print $field->name;
        print "</fieldset>";

        $this->DisplayTree( $field->code , $depth+8 );           
     }  

   }