MySQL group_concat WHERE 字段中的第一项具有特定 ID

Question

如何仅选择以特定 topic_id(“5000”)开始并包含多个 topic_id 的 session ？伪代码中的 WHERE 子句中的代码。

request_id  session_id  topic_id
1           1           3000
2           1           5000
3           2           5000
4           2           3000
5           2           6000
6           3           5000 

SELECT
min(request_id),
session_id,
group_concat(topic_id order by request_id asc SEPARATOR ' ,')
FROM requests
WHERE (first(topic_id) = '5000' AND count(topic_id) > 1)
group by session_id
order by request_id asc

result:
request_id  session_id  topic_id
3           2           5000, 3000, 6000

我知道这应该适用于子查询，但我不知道如何操作。谢谢!!

Answer 1

您可以使用 HAVING 子句将查询更改为如下所示

SELECT
request_id,
session_id,
group_concat(topic_id order by request_id)
FROM sessions 
GROUP BY session_id
HAVING MIN(topic_id) = '5000' 
AND COUNT(DISTINCT topic_id) > 1
ORDER BY request_id;