有內MySQL的SQL語句JOIN

Question

我有以下SQL語句

SELECT be.*, it.order_number 
FROM songs AS be 

INNER JOIN 
(
    SELECT song_id, order_number 
    FROM items 
    WHERE order_status = 1 
) it 
ON be.id = it.song_id 

INNER JOIN orders AS or 
ON it.order_number = or.order_number 

WHERE be.active = 0 

我似乎無法理解爲什麼這種說法不會產生任何結果。當我刪除以下行;

INNER JOIN orders AS or 
ON it.order_number = or.order_number 

它似乎產生的結果，我知道order_number在orders表確實存在 - 所以它顯然是不正確的語法，但我不知道從哪裏走？感謝幫助。

Answer 1

在這個特定情況下的問題是查詢中的or是保留字。您可以使用，如果你願意，但你必須引用它，像這樣

SELECT be.*, it.order_number 
FROM songs AS be 

INNER JOIN 
(
    SELECT song_id, order_number 
    FROM items 
    WHERE order_status = 1 
) it 
ON be.id = it.song_id 

INNER JOIN orders AS "or" 
ON it.order_number = "or".order_number 

WHERE be.active = 0 

但是總的來說，爲便於閱讀，我會避免這樣的名字。如果你必須引用它或者逃避它，那可能是一個壞名字。