mysql 子查询时使用union时，两侧子查询不能带()

问题遇到的现象和发生背景

使用UNION 合并子查询时，子查询带()报错

问题相关代码，请勿粘贴截图

SELECT
goods_kind_id,
shop_unique,
goods_kind_unique,
goods_kind_parunique,
goods_kind_name,
goods_kind_order,
goods_kind_picture,
1 AS same_type,
IFNULL(goods_kind_alias, "") AS goods_kind_alias,
edit_type,
kind_type,
valid_type
FROM
goods_kind
WHERE
shop_unique = "1536215939565"
AND kind_type = 2
AND valid_type = 1
AND goods_kind_parunique IN (
(SELECT
goods_kind_unique
FROM
goods_kind
WHERE
shop_unique = "1536215939565"
AND kind_type = 2
AND goods_kind_parunique = "0"
AND valid_type = 1
)
UNION
(
SELECT
0 AS goods_kind_unique
)
)
ORDER BY
goods_kind_order ASC

运行结果及报错内容

[Err] 1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UNION
(
SELECT
0 AS goods_kind_unique
)
)
ORDER BY
goods_kind_order' at line 31

我的解答思路和尝试过的方法

去掉 UNION 两侧的()可以运行成功
如下
**SELECT
goods_kind_id,
shop_unique,
goods_kind_unique
FROM
goods_kind
WHERE
shop_unique = "1536215939565"
AND kind_type = 2
AND valid_type = 1
AND goods_kind_parunique IN (
SELECT
goods_kind_unique
FROM
goods_kind
WHERE
shop_unique = "1536215939565"
AND kind_type = 2
AND goods_kind_parunique = "0"
AND valid_type = 1

UNION

    SELECT
        0 AS goods_kind_unique

)
ORDER BY
goods_kind_order ASC**

我想要达到的结果

为什么加上括号运行不成功，但是单独运行
(SELECT
goods_kind_unique
FROM
goods_kind
WHERE
shop_unique = "1536215939565"
AND kind_type = 2
AND goods_kind_parunique = "0"
AND valid_type = 1
)
UNION
(
SELECT
0 AS goods_kind_unique
)
可以成功

• 请看👉 ：mysql 中关于 union 查询多表排序的问题

能运行成功也是奇怪啊：

union
SELECT  0 AS goods_kind_unique

select 后面没有 from语句，是从哪一张表查询呢？

试下这种格式：

select * from 
(SELECT
goods_kind_unique
FROM
goods_kind
WHERE
shop_unique = "1536215939565"
AND kind_type = 2
AND goods_kind_parunique = "0"
AND valid_type = 1
) as t1
UNION
select * from 
(
SELECT
0 AS goods_kind_unique
) as t2

你UNION后面的内容属于重命名啊，为什么不直接放入上面的查询语句里面