Mysql - 双组

Question

我跟随查询：

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

计算每天添加的单词。

一切都很好，但我想数独特！注意word_id在最后一个raw中有14,14。这必须计为1。

我认为double group_by会削减它，但这似乎是一种错误的方法。

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

Answer 2

你只需要使用不同的地方，你会说些什么： 你会最终得到：   COUNT(distinct word_id)

Answer 3

将distinct添加到count()和group_concat()：

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