SQL min函数

我试图让两列,frequency而frequency - min(frequency)但是我看到的是第二列为零.什么可能是错的？

SELECT
    frequency, frequency - min(frequency)
    FROM
    words
GROUP BY id
ORDER BY frequency;

您的查询组由频率的唯一值组成.在每个这样的组中,最小频率只是频率本身,因此0在减去两者时总会得到.相反,您可以使用以下窗口版本min:

SELECT   frequency, frequency - MIN(frequency) OVER() AS diff
FROM     words
ORDER BY frequency