Mysql 如何在产品查询中插入GROUP_CONCAT

我在MySQL 8中有3个相关表:

CREATE TABLE `products` (
  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
  `title` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
  `status` enum('D','P','A','I') COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT 'D' COMMENT ' D => Draft, P=>Pending Review, A=>Active, I=>Inactive',
  `sale_price` int unsigned DEFAULT NULL,
...


CREATE TABLE `discount_product` (
  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
  `product_id` bigint unsigned NOT NULL,
  `discount_id` tinyint unsigned NOT NULL,
...  
  

CREATE TABLE `discounts` (
  `id` tinyint unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(100) COLLATE utf8mb4_unicode_ci NOT NULL,
  `active` tinyint(1) NOT NULL DEFAULT '0',
  `min_qty` int unsigned DEFAULT NULL,
  `max_qty` int unsigned DEFAULT NULL,
  `percent` decimal(7,2) unsigned NOT NULL,
  `description` mediumtext COLLATE utf8mb4_unicode_ci NOT NULL, 
...

我需要在第2栏中显示相关折扣的产品；

我有两个工作要求.占位符为‘Discount_Info Content’的第一名:

SELECT products.id, products.title, products.sale_price,
    GROUP_CONCAT('discount_info content') AS discount_info

    FROM products WHERE has_discount_price = 1 AND id = 13
    GROUP BY products.id, products.title, products.sale_price

和按产品ID提供的第二次折扣:

SELECT  CONCAT(discounts.name, ': ', discounts.min_qty, ': ', discounts.max_qty, ': ', discounts.percent)
  FROM discounts, discount_product WHERE discount_product.discount_id = discounts.id AND discount_product.product_id = 13

两个请求都可以.

但是，当我使用GROUP_CONCAT将第二个请求插入到第一个请求的‘discount_info content’占位符中时:

SELECT products.id, products.title, products.sale_price,
    GROUP_CONCAT(SELECT  CONCAT(discounts.name, ': ', discounts.min_qty, ': ', discounts.max_qty, ': ', discounts.percent)
  FROM discounts, discount_product WHERE discount_product.discount_id = discounts.id AND discount_product.product_id = 13) AS discount_info


    FROM products WHERE has_discount_price = 1 AND id = 13
GROUP BY products.id, products.title, products.sale_price

我收到错误:

SQL Error [1064] [42000]: 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 'FROM discounts, discount_product WHERE discount_product.discount_id = discounts.' at line 3

如果我从GROUP_CONCAT内部删除了SELECT，但得到了相同的错误.

我为什么会出现这个错误，以及如何修复它？ 看起来我误解了GROUP_CONCAT的工作原理.