如何直接從MySQL查詢中獲得兩個百分比的百分比？

Question

林計算首先使用此查詢男人和女人在我的數據庫的百分比：

SELECT sum(case when `gender` = 'M' then 1 else 0 end) as male 
    , sum(case when `gender` = 'F' then 1 else 0 end) as female 
FROM userinfo 
WHERE id in (10,1,5) 

然後在PHP我計算百分比。但是我想知道，有沒有辦法直接從查詢中獲得百分比？

Answer 1

SELECT sum(case when `gender` = 'M' then 1 else 0 end) as male 
    , 100*sum(case when `gender` = 'M' then 1 else 0 end)/count(*) as malepct 
    , sum(case when `gender` = 'F' then 1 else 0 end) as female 
    , 100*sum(case when `gender` = 'F' then 1 else 0 end)/count(*) as femalepct 
FROM userinfo 
WHERE id in (10,1,5) 

...假設你沒有（被零除）運行此在一個空行集

如果你如想要用-1代替無效（除以零）值使用

if(ifnull(count(*),0)>0,100*sum(case when `gender` = 'M' then 1 else 0 end)/count(*),-1) as malepct