問題，以便通過查詢

Question

我有如下表： -

id name parent_id 
1 ABC 0 
2 XYZ 0 
3 BB 1 
4 AA 1 
5 PQR 0 

我想查詢的該命令其顯示這樣的結果。

1 ABC 0 
4 AA 1 
3 BB 1 
5 PQR 0 
2 XYZ 0 

即父項目和子項目按升序排列，父項目名稱後跟子項目。

我使用這樣的查詢，但當我們按順序使用順序然後（沒有上升）確定，但我想要命名水平與名稱。

SELECT distinct `pp088_projects`.* , ( 
    SELECT LPAD(parent.id, 5, '0') 
     FROM `pp088_projects` parent 
     WHERE parent.id = `pp088_projects`.id 
     AND parent.parent_id = 0 
    UNION 
    SELECT CONCAT(LPAD(parent.id, 5, '0'), '.', LPAD(child.id, 5, '0')) 
     FROM `pp088_projects` parent 
     INNER JOIN `pp088_projects` child 
     ON (parent.id = child.parent_id) 
     WHERE child.id = `pp088_projects`.id 
     AND parent.parent_id = 0 
    UNION 
    SELECT CONCAT(LPAD(parent.id, 5, '0'), '.', LPAD(child.id, 5, '0'), '.', 
      LPAD(grandchild.id, 5, '0')) 
     FROM `pp088_projects` parent 
     INNER JOIN `pp088_projects` child ON (parent.id = child.parent_id) 
     INNER JOIN `pp088_projects` grandchild ON (child.id = grandchild.parent_id) 
     WHERE grandchild.id = `pp088_projects`.id AND parent.parent_id = 0) AS level 
    FROM `pp088_projects` , `pp088_project_users` 
    WHERE (`pp088_projects`.`id` = `pp088_project_users`.`project_id` 
    AND `pp088_project_users`.`user_id` = '1') 
    AND (`pp088_projects`.`completed_on` = '0000-00-00 00:00:00') 
    ORDER BY level 

Answer 1

由於您只有兩個深度級別，因此不需要遞歸（MySQL有限的支持）。通過id而不是簡單地命令：

SELECT * 
FROM  pp088_projects 
ORDER BY IF(parent_id, parent_id, id), parent_id, id 

見它sqlfiddle。

或者，如果你想通過名稱訂購：

SELECT  child.* 
FROM  pp088_projects child 
    LEFT JOIN pp088_projects parent ON child.parent_id = parent.id 
ORDER BY COALESCE(parent.name, child.name), parent.id, child.name 

見它sqlfiddle。