具有INNER JOIN的MySQL SQL语句

Question

我有以下SQL语句

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

我似乎无法理解为什么该语句不产生任何结果。 当我删除以下行时；

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

它似乎会产生结果，并且我知道order_number确实存在于orders表中-因此它的语法显然不正确，但是我不确定从何处去？ 感谢帮助。

Answer 1

在此特定实例中的问题是查询中的or保留字。 您可以根据需要使用它，但必须引用它，就像这样

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

通常，为了便于阅读，我会避免使用此类名称。 如果您必须引用它或将其转义，则可能是一个不好的名字。