带有 INNER JOIN 的 MySQL SQL 语句

Question

我有如下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

我似乎不明白为什么这个声明没有产生任何结果。当我删除以下行时；

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

它似乎产生了结果，而且我知道 order_number 确实存在于 orders 表中 - 所以它显然是不正确的语法，但我不确定该去哪里从这里？感谢您的帮助。

Answer 1

此特定实例中的问题是查询中的 或 是保留字。如果你愿意，你可以使用它，但你必须引用它，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

一般来说，为了可读性，我会避免使用这样的名称。如果你必须引用它或转义它，它可能是一个糟糕的名字。