SQL如何對兩個不同的where子句應用DateDiff

Question

這是我當前的查詢：

select serial_number, order_number,
(select TOP 1 PRODUCT_ID from PS_ORD_LINE PL 
where PL.ORDER_NO = WO.order_number 
and CAT_DESCR = 'SYSTEM' and ORD_LINE_STATUS = 'O' 
ORDER BY ORDER_INT_LINE_NO) as model,
(select datediff(minute, min(complete_time), min(start_time)) 
 from TRACKED_OBJECT_HISTORY TOH1 
 where TOH1.op_name IN ('Assembly', 'Pre-Final') 
 and TOH1.tobj_key = TOH.tobj_key) as waiting_time1,
from UNIT U
left join WORK_ORDER WO on U.order_key = WO.order_key
left join TRACKED_OBJECT_HISTORY TOH on TOH.tobj_key = U.unit_key
where WO.creation_time > '5/1/12' and WO.creation_time < '7/31/12'
group by serial_number, order_number, tobj_key

DateDiff中間的部分是我的問題。

因此， Assembly和Pre-Final是台掃描兩種不同的站名。 Assembly通常是在第一線，緊接着Pre-Final 。

我要做的是計算從單元掃描出Assembly到該單元掃描到Pre-Final之前的經過時間。 complete_time標記何時將單元從工作站中掃描出， start_time表示其被掃描時。

現在，我的查詢不起作用，因為start_time和complete_time引用Assembly因為它是第一站。 但是，我希望complete_time引用Assembly而我希望start_time引用Pre-Final 。

我應該怎么做呢？

Answer 1

也許使用

DATEDIFF(MINUTE,
         (SELECT MIN(complete_time)
            FROM TRACKED_OBJECT_HISTORY toh1 
            WHERE toh1.op_name = 'Pre-Final' AND toh1.tobj_key = toh.tobj_key),
         (SELECT MIN(start_time) 
            FROM TRACKED_OBJECT_HISTORY toh2
            WHERE toh2.op_name = 'Assembly' AND toh2.tobj_key = toh.tobj_key)
         ) AS waiting_time1,

等等

Answer 2

我不完全了解您的數據庫結構，但是如果您應該能夠使用子查詢為每個項目提取兩次。 這是代碼示例的示例，假設tobj_key引用一個對象，並且每個對象僅通過計算機一次。

SELECT
   DateDiff(n,AssemblyTime,PrefinalTime)
FROM (
   SELECT 
      tobj_key,
      complete_time AS 'AssemblyTime'
   FROM TRACKED_OBJECT_HISTORY
   WHERE op_name = 'Assembly'
   ) AS sub1
JOIN (
   SELECT 
      tobj_key,
      start_time AS 'PrefinalTime'
   FROM TRACKED_OBJECT_HISTORY
   WHERE op_name = 'Assembly'
   ) AS sub2 ON sub1.tobj_key = sub2.robj_key