需求：需統計出某個集合內，某個段所占的比例，涉及SELECT查詢語句的嵌套，如有疑問可留言。
如下：
--按性別進行年度掛號年齡段分析
--男
SELECT 年齡段,SUM(人數) 數量,cast(cast((SUM(人數)/((select count(*) from YXHIS2020..VTBMZGHMX2020 WHERE BTH=0 AND CXB='男')*1.0)*100) as decimal(9,2)) as varchar)+'%' 所占比例 FROM (
SELECT
CASE
WHEN 年齡 between 0 and 12 THEN '0-12 歲'
WHEN 年齡 between 13 and 24 THEN '13-24歲'
WHEN 年齡 between 25 and 36 THEN '25-36歲'
WHEN 年齡 between 37 and 48 THEN '37-48歲'
WHEN 年齡 between 49 and 60 THEN '49-60歲'
ELSE '60歲以上' END 年齡段, 人數,性別
FROM (
SELECT 年齡,人數,性別 FROM (
select DATEDIFF(year, DCSNY, DGH) 年齡,count(CNL) 人數,CXB 性別
from YXHIS2020..VTBMZGHMX2020 WHERE BTH=0 AND CXB='男' group by DATEDIFF(year, DCSNY, DGH),CXB )A GROUP BY A.年齡,A.人數,A.性別)A )B GROUP BY 年齡段
--女
SELECT 年齡段,SUM(人數) 數量,cast(cast((SUM(人數)/((select count(*) from YXHIS2020..VTBMZGHMX2020 WHERE BTH=0 AND CXB='女')*1.0)*100) as decimal(9,2)) as varchar)+'%' 所占比例 FROM (
SELECT
CASE
WHEN 年齡 between 0 and 12 THEN '0-12 歲'
WHEN 年齡 between 13 and 24 THEN '13-24歲'
WHEN 年齡 between 25 and 36 THEN '25-36歲'
WHEN 年齡 between 37 and 48 THEN '37-48歲'
WHEN 年齡 between 49 and 60 THEN '49-60歲'
WHEN 年齡>60 THEN '60歲以上'
ELSE '年齡錯誤' END 年齡段, 人數,性別
FROM (
SELECT 年齡,人數,性別 FROM (
select DATEDIFF(year, DCSNY, DGH) 年齡,count(CNL) 人數,CXB 性別
from YXHIS2020..VTBMZGHMX2020 WHERE BTH=0 AND CXB='女' group by DATEDIFF(year, DCSNY, DGH),CXB )A GROUP BY A.年齡,A.人數,A.性別)A )B GROUP BY 年齡段