如何在MySQL的單個查詢中選擇所有sub_category記錄及其main_category_name和parent_id？

Question

我的類別表正在尋找類似如下：

------------------------------------ 
id | name   | parent_id | 
------------------------------------ 
1 | Vehicles  | 0   | 
2 | Car Insurance | 1   | 
3 | Van Insurance | 1   | 
4 | PhoneRecharge | 0   | 
5 | prepaid  | 4   | 
6 | postpaid  | 4   | 

輸出應該如下所示：

--------------------------------------------------------- 
id | parent_id | main_category_name | sub_category_name| 
--------------------------------------------------------- 
2 | 1  | Vehicles   | Car Insurance | 
3 | 1  | Vehicles   | Van Insurance | 
5 | 4  | PhoneRecharge | prepaid   | 
6 | 4  | PhoneRecharge | postpaid   | 

如需獲取上述記錄，我需要儘量減少我的數據庫交互。所以我需要在單個查詢中實現上述數據。

Answer 1

在這裏你去：http://sqlfiddle.com/#!9/1b1a7a/14

SQL： SELECT * FROM category t1 INNER JOIN (SELECT * FROM category WHERE parent_id != 0) t2 ON t1.id = t2.parent_id

Answer 2

這應該工作：

SELECT 
    c.id AS cat_id, 
     parent.id AS parent_id, 
    parent.name AS main_category_name, 
    c.name AS sub_category_name 
FROM 
    category c JOIN category parent ON c.parent_id = parent.id