在Oracle SQL中按時間間隔聚合數據

Question

我有一組天氣溫度數據，每5分鐘記錄一次記錄。我想彙總這15分鐘的數據。要做到這一點，我需要按日期，小時和分鐘對時間間隔進行分組，以便在以下分鐘間隔{5,10,15}，{20,25,30}，{35， 40，45}，{50,55，60}。對於每組三個讀數，我應該取平均值。

我的數據有一個'DD-MMM-YY HH.MM'形式的時間戳，所以我提取了日期，小時和分鐘。我寫了一個案例來對時間戳進行分組，這並不是很正確，我不確定如何在平均函數中構建案例。

Select 
    Temperature, 
    Extract(Minute From Reading_Time) As Minutes, 
    Extract(Hour From Reading_Time) As Hours, 
    Cast(Reading_Time As Date) As Calendar_Date 
    From Weather_Data Where Weather_Station='BDX'  
    Case 
    When (Minutes>5 And Minutes<=15) Then 
    To_Timestamp(Calendar_Date &' '&'0'&Hours&':15', 'dd-mon-yy hh24:mi') 
    When (Minutes>20 And Minutes<=30) Then 
    To_Timestamp(Calendar_Date &' '&'0'&Hours&':30', 'dd-mon-yy hh24:mi') 
    When (Minutes>35 And Minutes<=45) Then 
    To_Timestamp(Calendar_Date &' '&'0'&Hours&':45', 'dd-mon-yy hh24:mi') 
    When (Minutes>50 And Minutes<=60) Then 
    To_Timestamp(Calendar_Date &' '&'0'&Hours&':60', 'dd-mon-yy hh24:mi') 
End 

修改後的代碼與戈登的反饋。我還重寫了案例邏輯以糾正時間上的輕微偏移。

select t.*, 
(Case When Minutes <= 15 AND Minutes > 0 
     Then To_Timestamp(Calendar_Date &' '&Hours&':15', 'dd-mon-yy hh24:mi') 
     When Minutes <= 30 AND Minutes > 0 
     Then To_Timestamp(Calendar_Date &' '&Hours&':30', 'dd-mon-yy hh24:mi') 
     When Minutes <= 45 AND Minutes > 0 
     Then To_Timestamp(Calendar_Date &' '&Hours&':45', 'dd-mon-yy hh24:mi') 
     When Minutes = 0 
     Then To_Timestamp(Calendar_Date &' '&Hours&':00', 'dd-mon-yy hh24:mi') 
     Else To_Timestamp(Calendar_Date &' '&(Hours+1)&':00', 'dd-mon-yy hh24:mi') 
    End) As Aggregated_Timestamp 
from (Select average(Temperature), Extract(Minute From Reading_Time) As Minutes, 
     Extract(Hour From Reading_Time) As Hours, Cast(Reading_Time As Date) As Calendar_Date 
    From Weather_Data 
    Where Weather_Station = 'BDX' 
    Group by Aggregated_Time 
) t 

Answer 1

您的case只是在您的查詢後徘徊。最簡單的寫法是用子查詢：

select t.*, 
     (Case When (Minutes>5 And Minutes<=15) 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':15', 'dd-mon-yy hh24:mi') 
      When (Minutes>20 And Minutes<=30) 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':30', 'dd-mon-yy hh24:mi') 
      When (Minutes>35 And Minutes<=45) 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':45', 'dd-mon-yy hh24:mi') 
      When (Minutes>50 And Minutes<=60) 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':60', 'dd-mon-yy hh24:mi') 
     End) 
from (Select Temperature, Extract(Minute From Reading_Time) As Minutes, 
      Extract(Hour From Reading_Time) As Hours, Cast(Reading_Time As Date) As Calendar_Date 
     From Weather_Data 
     Where Weather_Station = 'BDX' 
    ) t 

我不完全理解你的邏輯，因爲你有空白。我簡單地寫：

 (Case When Minutes <= 15 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':15', 'dd-mon-yy hh24:mi') 
      When Minutes <= 30 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':30', 'dd-mon-yy hh24:mi') 
      When Minutes <= 45 
      Then To_Timestamp(Calendar_Date &' '&'0'&Hours&':45', 'dd-mon-yy hh24:mi') 
      else To_Timestamp(Calendar_Date &' '&'0'&Hours&':60', 'dd-mon-yy hh24:mi') 
     End)