Скачать или смотреть How to Use Neo4j Cypher to Create Node Groups from CSV Data

Learn how to effectively group nodes in `Neo4j` based on CSV column values and generate relationships using Cypher queries.
---
This video is based on the question https://stackoverflow.com/q/74106369/ asked by the user 'Yamini-N' ( https://stackoverflow.com/u/20269308/ ) and on the answer https://stackoverflow.com/a/74106650/ provided by the user 'Graphileon' ( https://stackoverflow.com/u/1734996/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Neo4j Cypher to Yield groups of nodes based on CSV column value

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Introduction to the Problem

Importing data from CSV files into Neo4j can be a daunting task, especially when you're trying to organize that data into meaningful groups. In this guide, we'll explore how to create groups of nodes based on a specific column value from a CSV file.

Imagine you have a CSV file containing columns like Class, Level, Title, and Relationship. Your goal is to create distinct groups of nodes (set_A, set_B, etc.) based on the Relationship column value. Additionally, you want to leverage the flexibility of multiple node labels by using apoc.merge.node().

Let's dive into the solution.

Understanding the Original Query

You started with a query that attempted to create nodes according to different relationship types. Here's a simplified version of your original query:

[[See Video to Reveal this Text or Code Snippet]]

The Issue

The issue lies in the way the nodes are being created. Each conditional filter for the Relationship column effectively reduces the dataset available in the subsequent sections of the query. Consequently, when you check for set_B, it doesn’t find any rows because the context has been restricted by the previous WITH clause.

An Effective Solution

To effectively group nodes based on the Relationship column, you can modify your Cypher query to avoid filtering too early. Instead, you can collect nodes after merging without premature constraints. Here’s a refined version of your query:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Improved Query

Loading CSV: We are loading the CSV with headers, making it easier to reference column names.

Using WITH: We use a WITH clause to ensure we maintain the context of all rows in the CSV, rather than filtering them out too early.

Node Creation: The apoc.merge.node() function is called for each record, which merges nodes based on the Class and Level. The title is assigned dynamically, using coalesce to provide a default value when Title is missing.

Collecting Nodes: Finally, we return the Relationship value along with a collection of nodes created for each relationship type.

By using this structure, you can generate complete groups of nodes without losing context from your original dataset.

Conclusion

Now that you have a way to group nodes in Neo4j based on a CSV file, you can build relationships between these groups using further criteria. This approach gives you much more flexibility and power in organizing your data.

Feel free to try out the provided Cypher query in your Neo4j instance. If you have any further questions or run into any issues, don't hesitate to ask for help!