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select
count(*) as 人口总数,
sum(case when sex=0 then 1 else 0 end) 男人数,
sum(case when sex=0 then 1 else 0 end)*1.0/count(*)男所占比例,
sum(case when sex=1 then 1 else 0 end) 女人数,
sum(case when sex=1 then 1 else 0 end)*1.0 /count(*)女所占比例
from cj_yonghu
因为变量之间运算,如果没有指定类型,默认取整!
select
count(*) as 人口总数,
sum(case when sex=0 then 1 else 0 end) 男人数,
cast(cast(100.0*sum(case when sex=0 then 1 else 0 end)/count(*) as decimal(18,2)) as varchar(5))+'%' 男所占比例,
sum(case when sex=1 then 1 else 0 end) 女人数,
cast(cast(100.0*sum(case when sex=1 then 1 else 0 end)/count(*) as decimal(18,2)) as varchar(5))+'% 女所占比例
from cj_yonghu
select
count(*) as 人口总数,
sum(case when sex=0 then 1 else 0 end) 男人数,
1.0*sum(case when sex=0 then 1 else 0 end)/count(*) 男所占比例, --加上1.0,否则整数/整数取的还是整数
sum(case when sex=1 then 1 else 0 end) 女人数,
1.0*sum(case when sex=1 then 1 else 0 end)/count(*) 女所占比例
from cj_yonghu