Sql 两个select语句之间的数学运算

我目前正试图在我的postgres db中找到一定数量的预注册用户的百分比，操作将是

（1185*100）/3104=38.17

。为此，我使用两个select语句来检索每个计数，但我无法在它们之间进行操作：

+ count +
-  1185 -
-  3104 -

这就是我所拥有的：

select
    count(*)
    from crm_user_preregistred
    left join crm_player on crm_user_preregistred."document" = crm_player."document" 
    left join crm_user on crm_player.user_id = crm_user.id
    where crm_user.email is not null
union all
select
    count(*)
    from crm_user_preregistred

---

提前感谢您提供的任何提示或帮助。

您可以使用一些with子句简化您的选择，用count（*）选择替换值，可能对结果进行一些格式化，并在value2上检查0

with temp_value1 as (
   select 1185 as value1 ),
temp_value2 as (
select 3104 as value2 )

select (select temp_value1.value1::float * 100  from temp_value1) /
(select temp_value2.value2::float from temp_value2)

结果: 38.17654639175258

通过您的选择：

with temp_value1 as (
select
    count(*) as value1
    from crm_user_preregistred
    left join crm_player on crm_user_preregistred."document" = crm_player."document" 
    left join crm_user on crm_player.user_id = crm_user.id
    where crm_user.email is not null
),
temp_value2 as (
select
    count(*) as value2
    from crm_user_preregistred
)

select (select temp_value1.value1::float * 100  from temp_value1)  / (select temp_value2.value2::float from temp_value2)

---

您可以在一个查询中执行此操作：

select count(*) filter (where cu.email is not null) * 100.0 / max(cup.cnt)
from (select cup.*, count(*) over () as cnt
      from crm_user_preregistred cup
     ) cup left join
     crm_player cp
     on cup."document" = cp."document" left join
     crm_user cu
     on cp.user_id = cu.id
where cu.email is not null;

我怀疑查询可以进一步简化，但在不了解数据模型的情况下，很难提出具体建议