该应用程序的视图包含一个页面，其中显示了一堆旋转木马（每个旋转木马=一个标签），每个旋转木马应该包含5个产品:

+-------------------------------------+
|Page                                 |
|+-----------------------------------+|
||Tag1                               ||
||+--------+ +--------+    +--------+||
|||Product1| |Product2| .. |Product5|||
||+--------+ +--------+    +--------+||
|+-----------------------------------+|
|...                                  |
|+-----------------------------------+|
||TagN                               ||
||...                                ||
+-------------------------------------+

+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | varchar(16) | NO   | UNI | NULL    |                |
+-------+-------------+------+-----+---------+----------------+

CREATE TABLE `pages` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(16) COLLATE utf8mb4_unicode_ci NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

+--------------+------------+------+-----+---------+----------------+
| Field        | Type       | Null | Key | Default | Extra          |
+--------------+------------+------+-----+---------+----------------+
| id           | int(11)    | NO   | PRI | NULL    | auto_increment |
| page_id      | int(11)    | NO   | MUL | NULL    |                |
| tag_id       | int(11)    | NO   | MUL | NULL    |                |
| position     | tinyint(4) | NO   |     | NULL    |                |
+--------------+------------+------+-----+---------+----------------+

CREATE TABLE `pages_tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `page_id` int(11) NOT NULL,
  `tag_id` int(11) NOT NULL,
  `position` tinyint(4) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `page_id` (`page_id`),
  KEY `tag_id` (`tag_id`),
  CONSTRAINT `pages_tags_ibfk_1` FOREIGN KEY (`page_id`) REFERENCES `pages` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `pages_tags_ibfk_2` FOREIGN KEY (`tag_id`) REFERENCES `tags` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=663 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

+---------+--------------+------+-----+---------+----------------+
| Field   | Type         | Null | Key | Default | Extra          |
+---------+--------------+------+-----+---------+----------------+
| id      | int(11)      | NO   | PRI | NULL    | auto_increment |
| name    | varchar(128) | NO   |     | NULL    |                |
+---------+--------------+------+-----+---------+----------------+

CREATE TABLE `tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(128) COLLATE utf8mb4_unicode_ci NOT NULL,
  PRIMARY KEY (`id`),
) ENGINE=InnoDB AUTO_INCREMENT=149 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

+------------+---------+------+-----+---------+----------------+
| Field      | Type    | Null | Key | Default | Extra          |
+------------+---------+------+-----+---------+----------------+
| id         | int(11) | NO   | PRI | NULL    | auto_increment |
| product_id | int(11) | NO   | MUL | NULL    |                |
| tag_id     | int(11) | NO   | MUL | NULL    |                |
+------------+---------+------+-----+---------+----------------+

CREATE TABLE `products_tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `product_id` int(11) NOT NULL,
  `tag_id` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `tag_id` (`tag_id`),
  KEY `bouquet_id` (`product_id`),
  CONSTRAINT `products_tags_ibfk_1` FOREIGN KEY (`product_id`) REFERENCES `products` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `products_tags_ibfk_2` FOREIGN KEY (`tag_id`) REFERENCES `tags` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=5698 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| id          | int(11)      | NO   | PRI | NULL    | auto_increment |
| name        | varchar(128) | NO   | UNI | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

CREATE TABLE `products` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(128) COLLATE utf8mb4_unicode_ci NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=335 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

目标是得到一个输出，它将包含页面上的所有标签，每个标签最多包含5个产品。

下面是我在陷入困境之前得到的一个查询:

SELECT t.name, p.name 
FROM pages a 
LEFT JOIN pages_tags a_t ON a_t.page_id = a.id 
LEFT JOIN tags t ON t.id = a_t.tag_id 
LEFT JOIN products p ON p.id = (
  SELECT p_t.product_id FROM products_tags p_t WHERE p_t.tag_id = t.id LIMIT 1
);`

1. 无法使用限制5:

错误1242（21000）:子查询返回多行

错误1235（42000）:此版本的MySQL尚不支持“LIMIT和 在/All/Any/Some子查询中“

需要帮助。

• 页
  • 标记1
    • 产品1
    • 产品2
    • 产品3
    • 产品4
    • 产品5
    • 产品6
    • 产品7
    • 产品8
    • 产品9
    • 产品10
    • 产品K
    • 产品L（但始终为5的最大值）