mysql - COUNT 与 IF FROM DISTINCT 值 MySQL

Question

在对 UserID 执行 DISTINCT 之后，我正在尝试计算有多少用户是女性和多少男性

SELECT
COUNT(IF("Gender" = 'female', 1, NULL)) as Ufemale,
COUNT(IF("Gender" = 'male', 1, NULL)) as Umale
FROM (SELECT DISTINCT UserID FROM user_stats where Year='2019' and Account='P') as UID

如果我执行

SELECT DISTINCT UserID FROM user_stats where Year='2019' and Account='P'

它返回唯一的 UserID。但是，如果我将它与计数性别部分结合起来，它会返回零。

这是值的样子

UserID            |  Gender
-----------------------------
2018359084885123  |  male
1925823664195671  |  female
2033134076795519  |
2122445674469149  |  female
2315129265210413  |  female
2018359084885123  |  male
2122445674469149  |  female

目的是展示

Ufemale  |  Umale
-------------------
   3     |    1

Answer 1

试试这个:

表格

drop table if exists test;

create table test (userid bigint, gender char(6));

insert into test values
(2018359084885123,'male')
,(1925823664195671,'female')
,(2033134076795519, null)
,(2122445674469149,'female')
,(2315129265210413,'female')
,(2018359084885123,'male')
,(2122445674469149,'female');

查询

select
    sum(case when gender = 'female' then 1 else 0 end) as ufemale,
    sum(case when gender = 'male' then 1 else 0 end) as umale
from
(select distinct userid, gender from test) x

结果

ufemale umale
3       1

例子:https://rextester.com/JLQ19855