MySQL distinct count if conditions unique

Question

I am trying to build a query that tells me how many distinct women and men there are in a given dataset. The person is identified by a number 'tel'. It is possible for the same 'tel' to appear multiple times, but that 'tel's gender should only be counted one time!

7136609221 - male
7136609222 - male
7136609223 - female
7136609228 - male
7136609222 - male
7136609223 - female

This example_dataset would yield the following.
Total unique gender count: 4
Total unique male count: 3
Total unique female count: 1

My attempted query:

SELECT COUNT(DISTINCT tel, gender) as gender_count,         COUNT(DISTINCT tel, gender = 'male') as man_count,         SUM(if(gender = 'female', 1, 0)) as woman_count  FROM example_dataset; 

There's actually two attempts in there. COUNT(DISTINCT tel, gender = 'male') as man_count seems to just return the same as COUNT(DISTINCT tel, gender) -- it doesn't take into account the qualifier there. And the SUM(if(gender = 'female', 1, 0)) counts all the female records, but is not filtered by DISTINCT tels.

Answer 1

Here's one option using a subquery with DISTINCT:

SELECT COUNT(*) gender_count,    SUM(IF(gender='male',1,0)) male_count,    SUM(IF(gender='female',1,0)) female_count FROM (    SELECT DISTINCT tel, gender    FROM example_dataset ) t 

• SQL Fiddle Demo

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This will also work if you don't want to use a subquery:

SELECT COUNT(DISTINCT tel) gender_count,     COUNT(DISTINCT CASE WHEN gender = 'male' THEN tel END) male_count,       COUNT(DISTINCT CASE WHEN gender = 'female' THEN tel END) female_count FROM example_dataset 

• More Fiddle