在PostgreSQL中

Question

組錯誤我在PostgreSQL的9.4得到一組誤差範圍內：

錯誤：在需要GROUP有序集總排名 4號線：（選擇a1.rank爲r1，

create view a as (select rank() over (order by pid, time) 
    pid, event, time 
    from test5); 



select e1.prev, e1.event, count(*) 
from 
    eventtransitions as e1, 
    (select a1.rank as r1, 
     a2.rank as r2, 
     a1.event as a1_event, 
     a2.event as a2_event, 
     a1.pid as a1_pid, 
     a2.pid as a2_pid 
from a as a1, a as a2) as temp 
where r1 = r2-1 
and e1.event = a2_event 
and e1.prev = a1_event 
and a1_pid = a2_pid 
group by e1.prev, e1.event; 

這對我來說有點奇怪，因爲根據我對這個錯誤的理解，這意味着我需要爲我的聚合函數級別設置order by子句，但是我確實使視圖成爲了一個，並且我有order by子句在那裏，我該如何解決這個錯誤，以及我所做的假設是不正確的？

Answer 1

我認爲你的錯誤是在視圖中的錯字。我相信你想要的是這個什麼：

create view a as 
select 
    rank() over (order by pid, time), 
    pid, event, time 
from test5; 

因爲它代表當前視圖的定義：

create view a as (select rank() over (order by pid, time) 
    pid, event, time 
    from test5); 

實際發生的rank()功能和別名爲「PID」，這是這相當於：

create view a as (select rank() over (order by pid, time) as pid, 
    event, time 
    from test5); 

其結果是，當您在選擇查詢調用等級，它指的是功能，而不是場（其中做不存在，因爲你已經混淆了它）。