Question

我正在尝试选择一个带有子查询的查询，该子查询选择两个时间戳字段之间的增量。

例如Delta =时间戳N-时间戳N-1

{{1}}

这是我得到的错误：

信息512，级别16，状态1，第1行
子查询返回的值超过1。当子查询遵循=，！=，<，<=，>，> =或将子查询用作表达式时，不允许这样做。

Answer 1

您可以为此使用lag（）函数

select T_event.Actie_ID, actie_omschrijving, event_timestamp, left(custom1,4) as model, custom1, Custom2, 
       Lag(T_event.event_timestamp) over (order by T_event.Event_ID) - T_event.event_timestamp AS Delta
from T_event
  inner join T_Actie ON T_event.Actie_ID = T_Actie.Actie_ID
WHERE T_EVENT.Actie_ID in (48,49,43,31,36) 
  and Event_Timestamp >= '2019-07-22'
order by Event_timestamp DESC

Answer 2

您的子查询返回多个值。您必须使用TOP子句或应用适当的过滤条件，以确保该子查询仅返回一行。当您应用TOP时，请确保您正在应用正确的ORDER BY子句。

select TOP 1 datediff(day,B.event_timestamp, A.event_timestamp) AS timediff
        from t_event A, 
             t_event B 
        where B.Event_ID = A.Event_ID-1
        ORDER BY timediff

另一件事，我从您的查询中发现的是，您计算出的时间戳差异与外部查询无关。您必须使用外部查询EventID

select T_event.Actie_ID, actie_omschrijving, event_timestamp, left(custom1,4) as model, custom1, Custom2, 
       (select TOP 1 datediff(day,B.event_timestamp, outer.event_timestamp) as timediff 
        from t_event AS B 
        where outer.Event_ID = A.Event_ID-1
        ORDER BY timediff) as timestampdifference
from T_event as outer
  inner join T_Actie ON T_event.Actie_ID = T_Actie.Actie_ID
WHERE T_EVENT.Actie_ID in (48,49,43,31,36) 
  and Event_Timestamp >= '2019-07-22'
order by Event_timestamp DESC

Answer 3

实际上，您的内部子查询与外部查询无关，因此，每行输出n个行，这是不可接受的。因此，您查询的可能解决方案是：

select t.T_event.Actie_ID, t.actie_omschrijving, t.event_timestamp, left(t.custom1,4) as model, t.custom1, t.Custom2, 
       (select B.event_timestamp - A.event_timestamp   
        from t_event A, 
             t_event B 
        where B.Event_ID = A.Event_ID-1 
        and B.Event_ID=t.Event_ID)      ---- here it might be A.event_id.... depends on your input and expected output
from T_event as t
  inner join T_Actie ON t.Actie_ID = T_Actie.Actie_ID
WHERE t.Actie_ID in (48,49,43,31,36) 
  and Event_Timestamp >= '2019-07-22'
order by Event_timestamp DESC

如何选择2个时间戳之间的增量

3 个答案: