MySQL查詢建議

Question

我有一個MySQL表這樣的 -

ID NAME  PARENT 
===================== 
1  Class 0 
2  Math  1 
3  Physics 1 
4  Cooking 0 
5  Italian 4 
6  Chinese 4 

我想要一個查詢，會給我這個輸出 -

ID NAME 
===================== 
1  Class 
2  Math Class 
3  Physics Class 
4  Cooking 
5  Italian Cooking 
6  Chinese Cooking 

父母的名字將與孩子的名字被追加，像姓。因爲有PARENT是對ID敵不過

Answer 1

SELECT t1.ID, CONCAT(t1.NAME, ' ', t2.NAME) AS NAME 
FROM your_table t1 
INNER JOIN your_table t2 ON t1.PARENT = t2.ID 

Answer 2

LEFT JOIN需要在這種情況下。

SELECT a.ID, 
     CONCAT(a.Name, ' ', COALESCE(b.name,'')) Name 
FROM TableName a 
     LEFT JOIN TableName b 
      ON a.Parent = b.ID 

• SQLFiddle Demo

你也可以使用CONCAT_WS()這樣就可以省略COALESCE()

SELECT a.ID, 
     CONCAT_WS(' ', a.Name, b.name) Name 
FROM TableName a 
     LEFT JOIN TableName b 
      ON a.Parent = b.ID 

• SQLFiddle Demo