题解 | #统计每种性别的人数#

#解法1 用 case when 和like用法
/*select case
        when profile like '%,male' then 'male'
        else 'female' 
        end as gender,count(*)
from user_submit
group by gender*/

#解法2 用if
/* select if(profile like '%,male','male','female')
as gender,count(*)
from user_submit
group by gender */

#解法3 用函数
select substring(profile,15) as gender,			#substring（字段名，n，lenth）这个函数的目的是返回字段名第n个位置起的lenth长度的字符串，若不写lenth则默认后面全部返回
count(*)
from user_submit
group by gender;