mysql - 为什么我不能像在支持它的表上那样对递归视图发出相同的查询?
问题描述
我有一个tags
表,在它上面我从递归 CTE 定义了一个视图,其中包含 tags 表的所有列:
CREATE VIEW tags_paths AS
WITH RECURSIVE tag_path (id, created_at, updated_at, community_id, tag_set_id, wiki_markdown,
wiki, excerpt, parent_id, name, path) AS
(
SELECT id, created_at, updated_at, community_id, tag_set_id, wiki_markdown,
wiki, excerpt, parent_id, name, name as path
FROM tags
WHERE parent_id IS NULL
UNION ALL
SELECT t.id, t.created_at, t.updated_at, t.community_id, t.tag_set_id,
t.wiki_markdown, t.wiki, t.excerpt, t.parent_id, t.name,
concat(tp.name, ' > ', t.name) as path
FROM tag_path AS tp JOIN tags AS t ON tp.id = t.parent_id
)
SELECT * FROM tag_path
ORDER BY path;
tags
我可以很好地针对表发出这个查询:
SELECT tags.*, COUNT(posts.id) AS post_count
FROM `tags`
LEFT OUTER JOIN `posts_tags` ON `posts_tags`.`tag_id` = `tags`.`id`
LEFT OUTER JOIN `posts` ON `posts`.`community_id` = 2 AND `posts`.`id` = `posts_tags`.`post_id`
WHERE `tags`.`community_id` = 2 AND `tags`.`tag_set_id` = 3
GROUP BY tags.id ORDER BY COUNT(posts.id) DESC LIMIT 96 OFFSET 0;
但是,针对tags_paths
视图发出的等效查询:
SELECT tags_paths.*, COUNT(posts.id) AS post_count
FROM `tags_paths`
LEFT OUTER JOIN `posts_tags` ON `posts_tags`.`tag_id` = `tags_paths`.`id`
LEFT OUTER JOIN `posts` ON `posts`.`community_id` = 2 AND `posts`.`id` = `posts_tags`.`post_id`
WHERE `tags_paths`.`community_id` = 2 AND `tags_paths`.`tag_set_id` = 3
GROUP BY tags_paths.id ORDER BY COUNT(posts.id) DESC LIMIT 96 OFFSET 0;
作为错误返回,特别是:
[42000][1055] Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column
'tags_paths.created_at' which is not functionally dependent on columns in GROUP BY clause; this is
incompatible with sql_mode=only_full_group_by
为什么?我能做些什么呢?
解决方案
正如@Akina 所说id
,是 table 上的键tags
,而不是视图上的键。id
因此,按照 SQL 标准的规定,不能在视图中为其余列与该列建立直接依赖关系。
你有两个选择。您可以:
将所有列添加到
GROUP BY
子句。TEXT
有时这对于大型类型(例如二进制文件)是不可能的。或者,您可以聚合
SELECT
子句中的列。
下面是使用后者的修改后的 SQL 语句:
SELECT
tags_paths.id,
max(tags_paths.created_at) as created_at,
max(tags_paths.updated_at) as updated_at,
max(tags_paths.community_id) as community_id,
max(tags_paths.tag_set_id) as tag_set_id,
max(tags_paths.wiki_markdown) as markdown,
max(tags_paths.wiki) as wiki,
max(tags_paths.excerpt) as excerpt,
max(tags_paths.parent_id) as parent_id,
max(tags_paths.name) as name,
max(tags_paths.path) as path,
COUNT(posts.id) AS post_count
FROM `tags_paths`
LEFT OUTER JOIN `posts_tags` ON `posts_tags`.`tag_id` = `tags_paths`.`id`
LEFT OUTER JOIN `posts` ON `posts`.`community_id` = 2
AND `posts`.`id` = `posts_tags`.`post_id`
WHERE `tags_paths`.`community_id` = 2 AND `tags_paths`.`tag_set_id` = 3
GROUP BY tags_paths.id
ORDER BY COUNT(posts.id) DESC
LIMIT 96
OFFSET 0;
是的,它变得更长了。
推荐阅读
- javascript - 环回 | 用于加载数据的命令行参数
- spring-boot - Spring Boot 找不到 bean
- vb.net - 连接池真的能提高整体性能吗?
- javascript - ReactJS:动态添加标签和内容到 react-dom 并重新加载
- macos - 在 Applescript 中使用 sed 时,Sed“无效的命令代码 <”
- ruby - 使用 prometheus client_ruby 客户端报告队列大小
- html - 无法让 CSS 动画在 Shopify 中工作
- python - 有没有办法配置 UML 图在 PyCharm 中呈现方法(按名称)的方式?
- prestashop - Prestashop 1.7:如何将 CMS 页面设置为主页
- sql - plsql引号中的Oracle计划作业错误