DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Refcards Trend Reports
Events Video Library
Over 2 million developers have joined DZone. Join Today! Thanks for visiting DZone today,
Edit Profile Manage Email Subscriptions Moderation Admin Console How to Post to DZone Article Submission Guidelines
View Profile
Sign Out
Refcards
Trend Reports
Events
View Events Video Library
Zones
Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks

Integrating PostgreSQL Databases with ANF: Join this workshop to learn how to create a PostgreSQL server using Instaclustr’s managed service

Mobile Database Essentials: Assess data needs, storage requirements, and more when leveraging databases for cloud and edge applications.

Monitoring and Observability for LLMs: Datadog and Google Cloud discuss how to achieve optimal AI model performance.

Automated Testing: The latest on architecture, TDD, and the benefits of AI and low-code tools.

Related

  • Angular Component Tree With Tables in the Leaves and a Flexible JPA Criteria Backend
  • Crafting Mazes
  • Solving Unique Search Requirements Using TreeMap Data Structure
  • Python F-Strings

Trending

  • Message Construction: Enhancing Enterprise Integration Patterns
  • The Emergence of Cloud-Native Integration Patterns in Modern Enterprises
  • How To Aim for High GC Throughput
  • A Complete Guide to Open-Source LLMs
  1. DZone
  2. Data Engineering
  3. Databases
  4. Neo4j & Cypher: Creating Relationships Between a Collection of Nodes / Invalid input ‘[‘:

Neo4j & Cypher: Creating Relationships Between a Collection of Nodes / Invalid input ‘[‘:

Mark Needham user avatar by
Mark Needham
·
May. 08, 14 · Interview
Like (0)
Save
Tweet
Share
4.51K Views

Join the DZone community and get the full member experience.

Join For Free

When working with graphs we’ll frequently find ourselves wanting to create relationships between collections of nodes.

A common example of this would be creating a linked list of days so that we can quickly traverse across a time tree. Let’s say we start with just 3 days:

MERGE (day1:Day {day:1 })
MERGE (day2:Day {day:2 })
MERGE (day3:Day {day:3 })
RETURN day1, day2, day3

And we want to create a ‘NEXT’ relationship between adjacent days:

(day1)-[:NEXT]->(day2)-[:NEXT]->(day3)

The most obvious way to do this would be to collect the days into an ordered collection and iterate over them using FOREACH, creating a relationship between adjacent nodes:

MATCH (day:Day)
WITH day
ORDER BY day.day
WITH COLLECT(day) AS days
FOREACH(i in RANGE(0, length(days)-2) | 
  CREATE UNIQUE (days[i])-[:NEXT]->(days[i+1]))

Unfortunately this isn’t valid syntax:

Invalid input '[': expected an identifier character, node labels, a property map, whitespace, ')' or a relationship pattern (line 6, column 32)
"            CREATE UNIQUE (days[i])-[:NEXT]->(days[i+1]))"
                                ^

It doesn’t seem to like us using array indices where we specify the node identifier.

However, we can work around that by putting days[i] and days[i+1] into single item arrays and using nested FOREACH loops on those, something Michael Hunger showed me last year and I forgot all about!

MATCH (day:Day)
WITH day
ORDER BY day.day
WITH COLLECT(day) AS days
FOREACH(i in RANGE(0, length(days)-2) | 
  FOREACH(day1 in [days[i]] | 
    FOREACH(day2 in [days[i+1]] | 
      CREATE UNIQUE (day1)-[:NEXT]->(day2))))

Now if we do a query to get back all the days we’ll see they’re connected:

2014 04 19 07 32 37
Neo4j Identifier Database Tree (data structure) Syntax (programming languages) Data structure

Published at DZone with permission of Mark Needham, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Related

  • Angular Component Tree With Tables in the Leaves and a Flexible JPA Criteria Backend
  • Crafting Mazes
  • Solving Unique Search Requirements Using TreeMap Data Structure
  • Python F-Strings

Comments

Partner Resources

X

ABOUT US

  • About DZone
  • Send feedback
  • Careers
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 3343 Perimeter Hill Drive
  • Suite 100
  • Nashville, TN 37211
  • support@dzone.com

Let's be friends: