整数除法返回0

Question

我觉得我错过了一些明显的东西.我试图测试分发random().这是表格:

create table test (
  id int,
  random_float float,
  random_int int
);

这是我想要做的:

truncate table test;
insert into test (id)
values (generate_series(1,1000));
update test 
set
  random_float = random() * 10 + 1;
update test
set
  random_int = trunc(random_float);
select 
  random_int,
  count(random_int) as Count,
  cast( count(random_int) / max(id) as float) as Percent
from test
group by random_int
order by random_int;

但是,"Percent"列为每条记录返回零.我尝试将其转换为float,作为十进制,我尝试将random_int列更改为十进制而不是整数,总是相同的结果.

这是一个小提琴.

对于我做错了什么的任何见解？

Answer 1

您应该在划分之前进行投射,但也缺少子查询以从表中获取总计数.这是样本.

select 
  random_int,
  count(random_int) as Count,
  cast(count(random_int) as decimal(7,2)) / cast((select count(random_int) from test) as decimal(7,2)) as Percent
from test
group by random_int
order by random_int;