clickhouse leftjoin count(子表) 数量异常的问题

自看,不整排版

以文章和评论举例:
结构
A.id,A.title,A.content
B.id,B.a_id,B.content

需求:查出评论数量为0的文章

SELECT ANY
	A.id,
	ANY ( A.title ) AS title,
	ANY ( A.content ) AS content,
	ANY ( B.id ) AS b_id,
	count( B.id ) AS b_total 
FROM
	A
	LEFT JOIN B ON A.id = B.a_id 
GROUP BY
	A.id 
HAVING
	b_id = '';

说明:如果查询评论大于0的文字,只需要在having中添加b_id <> ‘’ 即可,此时 b_total 的数量是正确的.