题解 | #计算25岁以上和以下的用户数量#

本题主要考察条件语句的使用。

1. if语句

select 
	age_cut,
	count(*)
    from
        (
          select 
            if(age < 25,"25岁以下","25岁及以上") as age_cut
            from user_profile
        ) as test
	group by age_cut

2. case语句

select case
          	when age < '25' then "25岁以下"
          	when age >= '25' then "25岁及以上"
         	else "25岁以下"
         	end as age_cut , count(age_cut) as number
      		from user_profile
    	group by age_cut