count(case when )的用法

今天接觸到了 count(case when ……)的用法，挺棒的。

表數據:

編號             性別

ID	gender
7136609221	male
7136609222	male
7136609223	female
7136609228	male
7136609222	male
7136609223	female

 

 

 

   

 

 

 

語句：

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

 

 

http://stackoverflow.com/questions/19672001/mysql-distinct-count-if-conditions-unique