MySQL GROUP BY 没有给出期望的结果

Question

我必须将摘要显示为每个单元中的男性人数、女性人数。尝试了以下查询:

SELECT 
    unit,
    CASE gender
        WHEN 'Male' THEN COUNT(id)
    END AS 'male',
    CASE
        WHEN gender = 'Female' THEN COUNT(id)
    END AS 'female'
FROM
    admission_info
WHERE
    admission_date = '2017-04-15'
GROUP BY gender

这是 Fiddle显示输出。但我希望它在 1 行中显示单位名称、男性人数、女性人数。

Answer 1

SELECT unit, 
sum(CASE gender WHEN 'Male' THEN 1 else 0 END) AS 'male', 
sum(CASE WHEN gender='Female' THEN 1 else 0 END) AS 'female' 
FROM admission_info WHERE admission_date='2017-04-15'
group by unit