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Mark is a graph advocate and field engineer for Neo Technology, the company behind the Neo4j graph database. As a field engineer, Mark helps customers embrace graph data and Neo4j building sophisticated solutions to challenging data problems. When he's not with customers Mark is a developer on Neo4j and writes his experiences of being a graphista on a popular blog at http://markhneedham.com/blog. He tweets at @markhneedham. Mark is a DZone MVB and is not an employee of DZone and has posted 547 posts at DZone. You can read more from them at their website. View Full User Profile

Neo4j: Handling SUM's Scientific Notation

10.01.2012
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In some of the recent work I’ve been doing with neo4j the queries I’ve written have been summing up the values from multiple nodes and after a certain number is reached the value returned used scientific notation.

For example, in a cypher query like this:

START category = node:categories('category_id:1')

MATCH p = category-[:has_child*1..5]->subCategory-[:has_product]->product-[:sold]->sales

RETURN EXTRACT(n in NODES(p) : n.category_id?),subCategory.category_id, SUM(sales.sales)


I might get a result set like this:

+------------------------------------------------------------------------------------------------+
| EXTRACT(n in NODES(p) : n.category_id?)        | subCategory.category_id  | SUM(sales.sales)   |
+------------------------------------------------------------------------------------------------+
| ["246","254","255","3279",<null>,<null>]       | "3279"                   | 3.07213e07         |
| ["246","3649","3650","4362",<null>,<null>]     | "4362"                   | 1.023412e06        |
| ["246","287","291","308",<null>,<null>]        | "308"                    | 504712.5999448135  |
+------------------------------------------------------------------------------------------------+


I wanted to be able to add the first two rows together but still have them return separately which meant I needed to convert the values into decimal notation in order to do so.

I came across a Stack Overflow thread explaining how to do it in Ruby:

> "%f" % "3.07213e07"
=> "30721300.000000"

or

> "3.07213e07".to_f
=> 30721300.0

If we want to do the same thing in Java it’d read like this:

double d = Double.parseDouble("3.07213e07");
NumberFormat formatter = new DecimalFormat("###.#####");
String f = formatter.format(d);
System.out.println(f);
// returns 30721300

I couldn’t see a way to make the SUM function return in decimal notation but it’d be neat if there was a way to.

For now we have to apply some formatting on the result if we want to do any calculations with it.

 

Published at DZone with permission of Mark Needham, author and DZone MVB. (source)

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