SQL-LEAD函数

问题描述

我尝试使用以下代码：

 SELECT SkillTargetID,DateTime,lead(EventName,1) over (partition by EventName order by DateTime) as next_eventname,lead(ReasonCode,1) over (partition by ReasonCode order by DateTime) as next_ReasonCode
 FROM ucce1_awdb.dbo.Agent_State_Trace ast
 WHERE 
 EventName = 3 and
 ReasonCode= 0 and
 next_eventname = 0 and
 next_ReasonCode = 114

但是由于next_eventname和next_ReasonCode，我无法执行该查询。有人可以建议我该如何处理吗？

解决方法

您需要一个子查询：

SELECT SkillTargetID,DateTime,next_eventname,next_ReasonCode
FROM (SELECT ast.*
             lead(EventName) over (partition by EventName order by DateTime) as next_eventname,lead(ReasonCode) over (partition by ReasonCode order by DateTime) as next_ReasonCode
      FROM ucce1_awdb.dbo.Agent_State_Trace ast
     ) ast
WHERE EventName = 3 and
      ReasonCode= 0 and
      next_eventname = 0 and
      next_ReasonCode = 114

,

您不能使用select子句的where子句中定义的别名...，也不能使用where子句中的窗口函数。您需要将过滤移至外部查询：

SELECT *
FROM (
    SELECT 
        SkillTargetID,lead(EventName,1) 
            over(partition by EventName order by DateTime) as next_eventname,lead(ReasonCode,1) 
            over(partition by ReasonCode order by DateTime) as next_ReasonCode
    FROM ucce1_awdb.dbo.Agent_State_Trace ast
) t
WHERE 
    EventName = 3 
    AND ReasonCode= 0
    AND next_eventname = 0 
    AND next_ReasonCode = 114

请注意，我将 all 个过滤器移到了外部查询（不仅是那些应用于窗口计算的过滤器）：那是因为（可能！）您需要窗口函数来查看整个数据集，在应用过滤器之前。