SQL 获取带有类别和 post_tag 的 WordPress 帖子

Question

我想从数据库列表中导出带有类别和标签的帖子。我试过这个Wordpress SQL: get post category and tags，但它在我的 MySQL 5.7.27 上不起作用并出现错误

Expression #3 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'wpdev.c.name' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

我的预期结果会是一样的

+---------------+----------+----------------+
| post_id       | category | tags           |
|---------------+----------+----------------+
| 213           | news     | tag1,tag2,tag3 |
+---------------+----------+----------------+

我的声明是：

SELECT p.id, p.post_name, c.name, GROUP_CONCAT(t.name) 
FROM wp_posts p JOIN wp_term_relationships cr on (p.id=cr.object_id) 
JOIN wp_term_taxonomy ct on (ct.term_taxonomy_id=cr.term_taxonomy_id and ct.taxonomy='category') 
JOIN wp_terms c on (ct.term_id=c.term_id) 
JOIN wp_term_relationships tr on (p.id=tr.object_id) 
JOIN wp_term_taxonomy tt on (tt.term_taxonomy_id=tr.term_taxonomy_id and tt.taxonomy='post_tag') 
JOIN wp_terms t on (tt.term_id=t.term_id) 
GROUP BY p.id

提前致谢。

Answer 1

如果您将聚合函数用作GROUP_CONCAT，则必须对结果中的所有非聚合列使用GROUP BY。
因此，将GROUP BY p.id 更改为GROUP BY p.id, p.post_name, c.name，错误就会消失。

要获取有关only_full_group_by 模式的更多信息，例如，您可以阅读此What are the benefits of only_full_group_by mode?。