MySQL的 - 轉換表導致成行

Question

我有一個表格式

id1 | id2 | id3 | id4 | id5 
a | b | c | null | null 
a | b | d | null | null 
a | b |null | null | null 

我需要的結果(a,b,c,d)

我做這個用PHP，但代碼太困難了......

<?php 
    $sql="SELECT t1.id as id1, t2.id AS id2, t3.id AS id3, t4.id AS id4, t5.id AS id5 
    FROM store_subcategory AS t1 
    LEFT JOIN store_subcategory AS t2 ON t2.parent_id = t1.id 
    LEFT JOIN store_subcategory AS t3 ON t3.parent_id = t2.id 
    LEFT JOIN store_subcategory AS t4 ON t4.parent_id = t3.id 
    LEFT JOIN store_subcategory AS t5 ON t5.parent_id = t4.id 
    WHERE (t1.root_id=$cat or t1.id=$cat) and t1.store_id=$id"; 

    $result=$mysqli->query($sql); 
    $subid=array(); 
    while($row=$result->fetch_assoc()) 
    { 
     if($row["id1"]!=null) $subid[$row["id1"]]=1; 
     if($row["id2"]!=null) $subid[$row["id2"]]=1; 
     if($row["id3"]!=null) $subid[$row["id3"]]=1; 
     if($row["id4"]!=null) $subid[$row["id4"]]=1; 
     if($row["id5"]!=null) $subid[$row["id5"]]=1; 
    } 
    $subsarray=array(); 
    foreach($subid as $key => $value) 
    { 
     array_push($subsarray, $key); 
    } 
    $subid=implode(",", $subsarray); 
    ?> 

感謝 PS：對不起，我的英語不好

編輯： 表是與5級

的層次化樹

`store_subcategory` (
    `id` int(11) NOT NULL AUTO_INCREMENT, 
    `parent_id` int(11) DEFAULT NULL, 
    `it` varchar(255) NOT NULL, 
    PRIMARY KEY (`id`) 

EDIT2： 的解決方案可能是這個

SELECT * FROM (
SELECT DISTINCT(t1.id) 
    FROM store_subcategory AS t1 
    WHERE (t1.root_id=$cat or t1.id=$cat) and t1.store_id=$id 
UNION 
SELECT DISTINCT(t2.id) 
    FROM store_subcategory AS t1 
    LEFT JOIN store_subcategory AS t2 ON t2.parent_id = t1.id 
    WHERE (t1.root_id=$cat or t1.id=$cat) and t1.store_id=$id 
UNION 
SELECT DISTINCT(t3.id) 
    FROM store_subcategory AS t1 
    LEFT JOIN store_subcategory AS t2 ON t2.parent_id = t1.id 
    LEFT JOIN store_subcategory AS t3 ON t3.parent_id = t2.id 
    WHERE (t1.root_id=$cat or t1.id=$cat) and t1.store_id=$id 
UNION 
SELECT DISTINCT(t4.id) 
    FROM store_subcategory AS t1 
    LEFT JOIN store_subcategory AS t2 ON t2.parent_id = t1.id 
    LEFT JOIN store_subcategory AS t3 ON t3.parent_id = t2.id 
    LEFT JOIN store_subcategory AS t4 ON t4.parent_id = t3.id 
    WHERE (t1.root_id=$cat or t1.id=$cat) and t1.store_id=$id 
UNION 
SELECT DISTINCT(t5.id) 
    FROM store_subcategory AS t1 
    LEFT JOIN store_subcategory AS t2 ON t2.parent_id = t1.id 
    LEFT JOIN store_subcategory AS t3 ON t3.parent_id = t2.id 
    LEFT JOIN store_subcategory AS t4 ON t4.parent_id = t3.id 
    LEFT JOIN store_subcategory AS t5 ON t5.parent_id = t4.id 
    WHERE (t1.root_id=$cat or t1.id=$cat) and t1.store_id=$id 
) AS t_group WHERE id IS NOT NULL 

Answer 1

我不知道該數據結構是如何有用的，但它聽起來像你想要類似於：

SELECT DISTINCT(ID) 
FROM 
    (select distinct(id1) AS ID 
    from table 
    UNION 
    select distinct(id2) AS ID 
    from table 
    UNION 
    select distinct(id3) AS ID 
    from table)