sql - 引用子选择之外的别名

Question

下面描述了我想用这个表做什么 左边是一个表，我想从中计算每个事件的“current_value”
代码 1 将 current_value 重置为 value
代码 2 将 value 添加到 current_value
Code3 用 value 减少 current_value

Table Events                        |column to be calculated                                
eventId  deviceId EventCode value   |current_value                              
1          1        1          2    |2                          
2          1        2          1    |3                          
3          1        2          1    |4                          
4          1        2          1    |5                              
5          1        3          2    |3                              
6          1        2          2    |5                              
7          1        1          1    |1                              
8          1        2          2    |3          code 1: set                     
9          1        2          1    |4          code 2: add                     
10         1        2          1    |5          code 3: subtract                        
11         1        3          3    |2                              

我的 SQL 代码看起来像

Select                                                  
    EventId,                                                
    deviceId,                                               
    (select last(value) from Events as E where E.EventCode = 1 and E.DeviceID = DeviceID and E.EventId<EventId) AS LastSetValue,                                                
    (select last(value) from Events as E where E.EventCode = 1 and E.DeviceID = DeviceID and E.EventId<EventId) AS FromEventID,                                             
    (select sum(value) from Events as E where E.EventCode = 2 and E.DeviceID = DeviceID and E.EventId between fromEventId and EventId) AS SumOfAdded,                                               
    (select sum(value) from Events as E where E.EventCode = 3 and E.DeviceID = DeviceID and E.EventId betweein FromEventId and EventId) AS SumOfSubtracted,                                             
    LastSetValue+SumOfAdded-SumofSubtracted as current_value                                                
from Events;

此代码似乎不起作用，因为在子选择部分 DeviceID 看起来是内部临时表 DeviceID，当我为外部 DeviceID 设置别名时，这也不起作用，因为找不到它。从EventID也有这个问题。

任何帮助这里有什么问题将不胜感激。

Answer 1

我不确定我 100% 理解你的问题，但如果我没看错，你应该只需要像这样给外部表起别名：

Select                                                  
    t.EventId,                                                
    t.DeviceId,                                               
    (select last(value) from Events as E where E.EventCode = 1 and E.DeviceID = t.DeviceID and E.EventId<t.EventId) AS LastSetValue,                                                
    (select last(value) from Events as E where E.EventCode = 1 and E.DeviceID = t.DeviceID and E.EventId<t.EventId) AS FromEventID,                                             
    (select sum(value) from Events as E where E.EventCode = 2 and E.DeviceID = t.DeviceID and E.EventId between fromEventId and t.EventId) AS SumOfAdded,                                               
    (select sum(value) from Events as E where E.EventCode = 3 and E.DeviceID = t.DeviceID and E.EventId between FromEventId and t.EventId) AS SumOfSubtracted,                                             
    LastSetValue+SumOfAdded-SumofSubtracted as current_value                                                
from Events t;