我如何获得一个组的mysql总行数的百分比? [英] How can I get the percentage of total rows with mysql for a group?

问题描述

下面我有一个查询，将从用户代理表和IP地址链接表中获取网站的最常见用户代理:

below I have a query that will get the most common user agents for a site from a table of user agents and a linked table of ip addresses:

SELECT count(*) as num, string FROM `useragent_ip`
left join useragents on useragent_id = useragents.id
group by useragent_id
having num > 2
order by num desc, string

有时它会向我显示类似的东西

Sometimes it will show me something like

25 Firefox
22 IE
11 Chrome
3  Safari
1  Spider 1
1  Spider 2
1  Spider 3

我的问题是，是否有一种方法可以使既然左侧的数字代表一个整体的百分比，并且会随着时间而增长，那么我能否使用sql语句的一部分来显示每个组在整体中的百分比?这样一来，不用使用having num > 2，我可以做些事情，说获得总行数的百分比，而不仅仅是行数?

My question is if there is a way that since the numbers on the left represent percentages of a whole, and will grow with time, can I have part of the sql statement to show each group's percentage of the whole? So that instead of using having num > 2 then I could do something that would say get the percentage of the total rows instead of just the number of rows?

推荐答案

是的，您可以:

select num, string, 100 * num / total as percent
from (
    select count(*) as num, string
    from useragent_ip
    left join useragents on useragent_id = useragents.id
    group by useragent_id) x
cross join (
    select count(*) as total
    from useragent_ip
    left join useragents on useragent_id = useragents.id) y
order by num desc, string;

我删除了having num > 2，因为它似乎没有意义.

I removed the having num > 2, because it didn't seem to make sense.

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