多JOIN視圖上相同的表

Question

我有這個DB存儲傳感器採集數據，
收購（ACQ）來自以固定間隔（日期時間）
每個採集具有存儲在數據許多不同的措施不同的控制單元（CU）表

acq 
    id 
    datetime 
    id_cu  

data   
    id   
    id_acq 
    id_meas 
    value 

，我需要這樣的觀點：

+---------------------+------+----+-----+ 
|  datetime  | v1 | v2 | v3 | 
+---------------------+------+----+-----+ 
| 2010-09-13 00:05:00 | 40.9 | 1 | 0.3 | 
| 2010-09-13 00:10:00 | 41.0 | 2 | 0.3 | 
| 2010-09-13 00:15:00 | 41.1 | 4 | 0.3 | 
+---------------------+------+----+-----+ 

AS：

• V1是data.value（例如，溼度）
  WHERE acq.id_cu = 1 AND data.id_meas = 100

• v2是data.value（例如，計數器）
  WHERE ACQ。 id_cu = 2且data.id_meas = 200

• v3是data.value（例如溫度）
  WHERE acq.id_cu = 3 AND data.id_meas = 300

等多達幾十種組合的用戶choosen

我結束了與此查詢，但它永遠呈現相比，一個將在生產

SELECT a1.datetime, d1.value, d2.value, d3.value 
FROM 
    acq a1, data d1 
    JOIN acq a2, data d2 
     ON a2.id=d2.id_acq AND a2.datetime=a1.datetime 
    JOIN acq a3, data d3 
     ON a3.id=d3.id_acq AND a3.datetime=a1.datetime 
WHERE a1.id=d1.id_acq 
    AND a1.id_cu=1 AND d1.id_meas=100 
    AND a2.id_cu=2 AND d2.id_meas=200 
    AND a3.id_cu=3 AND d3.id_meas=300 

數據量非常小我想這將更快地獲得每個a1.id_centr=x AND d1.id_meas=y條件的數據，然後按照我想要的方式打印數據。

什麼是最好（和正確）的方式來實現這一目標？

編輯：假設沒有在收購沒有我的意思是運行以下命令：

SELECT datetime, value 
FROM acq, data 
WHERE acq.id=data.id_acq 
    AND (
     id_cu=1 AND id_meas=100 
     OR id_cu=2 AND id_meas=200 
     OR id_cu=3 AND id_meas=300 
    ) 
ORDER BY id_cu, id_meas 

通過id_cu/id_meas更改和使用的編程語言（如Python + numpy的）顯示並排結果一側的分裂結果是物質的幾秒鐘與...分鐘的關係？

Answer 1

*假設DATETIME和data.id_acq Cu和id_meas都有指標*，你可以嘗試用虛擬列佔位符和kludgey MAX（）UNION查詢。如果你的data.values不是負數（如果他們是你可以簡單地選擇一個非常大的負數而不是零作爲虛擬佔位符值，這個數字超出了可能的範圍）：

select FOO.datetime, max(FOO.v1), max(FOO.v2), max(FOO.v3) 
    from 
    (

    select acq.datetime, data.value as v1,0 as v2, 0 as v3 
    from acq inner join data on acq.id = data.id_acq 
    where acq.id_cu=1 and data.id_meas=100 

    UNION 

    select acq.datetime, 0 as v1, data.value as v2, 0 as v3 
    from acq inner join data on acq.id = data.id_acq 
    where acq.id_cu=2 and data.id_meas=200 

    UNION 

    select acq.datetime, 0 as v1, 0 v2, data.value as v3 
    from acq inner join data on acq.id = data.id_acq 
    where acq.id_cu=3 and data.id_meas=300 
    ) as FOO 
    group by FOO.datetime 

Answer 2

你的JOINS是有點混淆（因爲你是顯式混合隱式）;試試這個：

SELECT a1.datetime, d1.value, d2.value, d3.value 
FROM 
    acq a1 
     INNER JOIN data d1 ON a1.id=d1.id_acq 
     INNER JOIN acq a2 ON a2.datetime=a1.datetime 
     INNER JOIN data d2 ON a2.id=d2.id_acq 
     INNER JOIN acq a3 ON a3.datetime=a1.datetime 
     INNER JOIN data d3 ON a3.id=d3.id_acq 
WHERE 1=1 
    AND a1.id_centr=1 AND d1.id_meas=100 
    AND a2.id_centr=2 AND d2.id_meas=200 
    AND a3.id_centr=3 AND d3.id_meas=300