SQL计数唯一出现的性别

Question

我有3张表（人口统计），（LINK）和（入场）

SELECT SUM(CASE dmg.dmg_Sex WHEN 'Male' THEN 1 END) AS male,
       SUM(CASE dmg.dmg_Sex WHEN 'Female' THEN 1 END) AS female,
FROM Demographic dmg
JOIN LINK lnk ON lnk.lnk_dmgID = dmg.dmg_ID
JOIN Admission adm ON adm.adm_ID = lnk.lnk_admID
WHERE adm.adm_ReferralDate >= '01/01/2011' AND adm.adm_ReferralDate <= '31/03/2011'

我试图在日期范围内总结性别。 这不行，我是在正确的轨道上吗？

只是在没有SUM和CASE的情况下执行普通查询100％。

Answer 1

SELECT SUM(CASE dmg.dmg_Sex WHEN 'Male' THEN 1 END) AS male,
       SUM(CASE dmg.dmg_Sex WHEN 'Female' THEN 1 END) AS female
FROM Demographic dmg
JOIN LINK lnk ON lnk.lnk_dmgID = dmg.dmg_ID
JOIN Admission adm ON adm.adm_ID = lnk.lnk_admID
WHERE adm.adm_ReferralDate >= '01/01/2011' AND adm.adm_ReferralDate <= '31/03/2011'

Answer 2

使用GROUP BY

SELECT dmg.dmg_Sex, COUNT (dmg.dmg_Sex)
FROM Demographic dmg
JOIN LINK lnk ON lnk.lnk_dmgID = dmg.dmg_ID
JOIN Admission adm ON adm.adm_ID = lnk.lnk_admID
WHERE adm.adm_ReferralDate >= '01/01/2011' 
AND adm.adm_ReferralDate <= '31/03/2011'
GROUP BY dmg.dmg_Sex