Mysql - 双组依据

Question

我有以下查询:

SELECT DATE(created) AS con_date,
       COUNT(*) AS con_per_day,
       GROUP_CONCAT(word_id)
FROM connections
WHERE created > (NOW() - INTERVAL 30 DAY)
GROUP BY con_date

计算每天添加的字数。

一切都很好，但我想计算唯一数!注意 word_id 在最后一个原始文件中有 14,14。这必须算作 1。

我以为双 group_by 会削减它，但它似乎是一种错误的方式。

有什么想法吗？

Answer 1

使用distinct

    SELECT DATE(created) AS con_date,           COUNT(distinct word_id) AS con_per_day,           GROUP_CONCAT(word_id)    FROM connections    WHERE created > (NOW() - INTERVAL 30 DAY)    GROUP BY con_date