SQL JOIN父母和孩子和GET父母和孩子记录计数

Question

我有这个查询，这给我很难找出问题，你的建议表示赞赏。

SELECT 
    cooperatives.island, cooperatives.id, 
    COUNT(
    CASE WHEN members.gender = 'Male' THEN 1 ELSE NULL END 
) AS males, 
    COUNT(
    CASE WHEN members.gender = 'Female' THEN 1 ELSE NULL END 
) AS females, 
    COUNT(members.gender) AS genderall 
FROM 
    cooperatives 
JOIN members ON cooperatives.id= members.c_id 
WHERE 
    1 = 1 
GROUP BY 
    cooperatives.island 

什么我试图做的是让导致这样

SQL result

这是工作，但我需要添加有另一列，它会显示一些合作社从各岛。

Answer 1

我怀疑你想：

SELECT c.island, COUNT(DISTINCT c.id) as num_cooperatives, 
     SUM(m.gender = 'Male') AS males, 
     SUM(m.gender = 'Female') AS females, 
     COUNT(m.gender) AS genderall 
FROM cooperatives c JOIN 
    members m 
    ON c.id = m.c_id 
GROUP BY c.island;