如何在Neo4j中使用密码查询为多列聚合函数 [英] How to do aggregate functions for multiple columns using cypher query in Neo4j

问题描述

我在图数据库中创建了2个节点，始发机场和目的地机场.它与名为"delayed_by"的属性相关.

I have 2 nodes created in graph database, origin airport and destination airport. It is related by a property named 'delayed_by'.

   MATCH (origin:origin_airport {name: row.ORIGIN}), 
   (destination:dest_airport {name: row.DEST})
   CREATE (origin)-[:delayed_by {carr_delay: row.carr_delay}]->(destination)
   CREATE (origin)-[:delayed_by {weather_delay: row.weather_delay}]->    
   (destination)
   CREATE (origin)-[:delayed_by {nas_delay: row.nas_delay}]->(destination)

delayed_by保留由于载波延迟，天气延迟和nas延迟引起的值延迟.在这里，我需要对起点和目的地进行分组，并使用Neo4j中的密码查询来计算所有3个延迟之和的平均值.我的输入文件以表格格式表示，其格式如下:

delayed_by holds the value delays caused due to carrier delay, weather delay and nas delay. Here I need to group_by origin and destination and calculate the average value of sum of all 3 delays using cypher query in Neo4j. Representing in tabular format, my input file will of the format as described below:

  ORIGIN    DEST    carr_delay  weather_delay   nas_delay
   ABE        ATL      492         56             56    
   ABE        DTW      412         0              47    
   ABQ        ATL      181         0              218   

我希望结果采用以下格式.

I am expecting the result in the below format.

  ORIGIN    DEST     Avg_delay  
   ABE        ATL      201.33          
   ABE        DTW      153         
   ABQ        ATL      133         

我正在使用以下查询:

     MATCH (oa:origin_airport)-[d:delayed_by]->(da:dest_airport)
     RETURN oa.name  AS Origin, da.name AS Destination,            
     AVG((toFloat(d.carr_delay))+(toFloat(d.weather_delay))+ 
     (toFloat(d.nas_delay))) As avg_delay
      ORDER BY avg_delay DESC
      LIMIT 10

但是获取Avg_delay的空值.

But getting null values for Avg_delay.

    ORIGIN  DEST     Avg_delay  
     ABE     ATL       NULL
     ABE     DTW       NULL
     ABQ     ATL       NULL

推荐答案

1)我建议更改模型:为延迟关系添加delay的属性类型，并将delay值保存在属性值中.

1) I recommend to change the model: for the delay relationship add the property type of delay, and the delay value save in the property value.

MATCH (origin:origin_airport {name: row.ORIGIN}), 
      (destination:dest_airport {name: row.DEST})
   CREATE (origin)
          -[:delayed_by {type: "carr_delay", value: row.carr_delay}]->
          (destination)
   CREATE (origin)
          -[:delayed_by {type: "weather_delay", value: row.weather_delay}]->
          (destination)
   CREATE (origin)
          -[:delayed_by {type: "nas_delay", value: row.nas_delay}]->
          (destination)

2)和所需的查询:

MATCH (oa:origin_airport)-[d:delayed_by]->(da:dest_airport)
RETURN oa.name  AS Origin, 
       da.name AS Destination,            
       AVG( toFloat(d.value) ) As avg_delay
ORDER BY avg_delay DESC
LIMIT 10

这篇关于如何在Neo4j中使用密码查询为多列聚合函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！