如何獲取Postgresql中子查詢返回的結果總數？

Question

我想獲得從子查詢返回的結果的總數。這是我的查詢：

select 
    count(r.reason_id) as num, 
    cast (count(r.reason_id) as float)/(select count(*) as total from r) * 100.0 as pct 
from (
    select 
     case 
      when rarreason != 0 then rarreason 
      else rejectreason end as reason_id 
    from 
     workorderlines 
    where 
     (rarreason != 0 or rejectreason != 0) 
    ) as r 

group by 
    r.reason_id 

然而，當我嘗試執行此，我得到這個錯誤：

ERROR: relation "r" does not exist 
LINE 3: ...on_id) as float)/(select count(*) as total from r) * 100.0... 
                  ^

********** Error ********** 

ERROR: relation "r" does not exist 
SQL state: 42P01 
Character: 112 

我該怎麼辦呢？我正在使用Postgresql 9.1。謝謝！

Answer 1

沒有檢查你的邏輯，但你可以重新安排它是這樣的：

with r as (
    select 
     case 
      when rarreason != 0 then rarreason 
      else rejectreason end as reason_id 
    from 
     workorderlines 
    where 
     (rarreason != 0 or rejectreason != 0) 
) 
select 
    count(r.reason_id) as num, 
    cast (count(r.reason_id) as float)/(select count(*) as total from r) * 100.0 as pct 
from r 
group by r.reason_id 

Answer 2

嘗試：

select 
    count(r.reason_id) as num, 
    cast (count(r.reason_id) as float)/max(r.count_all) * 100.0 as pct 
from (
    select 
     case 
      when rarreason != 0 then rarreason 
      else rejectreason end as reason_id, 
     count(*) over() as count_all 
    from 
     workorderlines 
    where 
     (rarreason != 0 or rejectreason != 0) 
    ) as r 

group by 
    r.reason_id