统计男女生人数--sql

统计男女生人数--sql

传统方法

-- 男性人口
SELECT pref_name AS 地区,
SUM(population) AS 男
FROM `user`
WHERE u_sex = '1'
GROUP BY pref_name;

-- 女性人口
SELECT pref_name AS 地区,
SUM(population) AS 女
FROM `user`
WHERE u_sex ='2'
GROUP BY pref_name;

CASE表达式

-- 统计 人口数据
SELECT pref_name AS 地区,
--  男性人口
SUM(CASE 	WHEN u_sex='1' THEN population	ELSE	0 END ) AS 男,
--  女性人口
SUM(CASE 	WHEN u_sex='2' THEN population	ELSE	0 END ) AS 女
FROM `user`
GROUP BY pref_name

图例