CODEWITHSUNDEEP
javaneo4jneo4j-cql
user2782746
user2782746

Reputation:

How to create one to many relationships in neo4j graph in most efficient way?

I am currently new to neo4j and exploring with cypher queries for a task at hand. I am using neo4j bolt driver in Java Here is what I am trying to achieve. I have something like below data available as a Java ArrayList(stored in a HashMap):

employerId 2 : [employeeId 1, employeeId 2, employeeId3, ...]

Which basically shows relationship between employer and employee (these are the employees of employer 2)

Now, I need to find these employees & employer in the graph(they may or may not exist already) and create a "(x:Employer) -[Employs]->(y:Employee)" relationship between them.

One way (maybe, naive) that I can think of, is to search for employer and employee every time and run a separate CREATE query for each.

match (employer:Employer{name:"John"}), (name:Employee{name:"Snow"}) CREATE (employer)-[pr:EMPLOYES]->(employee)

But I feel that it would unnecessary search for the same Employer node multiple times. And as time is an important criterion for me right now, I am looking for a better way(if exists)

As a newbie to neo4j, all I can think of is, to do a search for the employer ID once, and then run multiple queries using that result, with Employee ID being searched every time. But I am unable to find the correct query to do this. Moreover, will this be the right approach? I need to prepare this query from Java. So should I query multiple times or send a single query?

Upvotes: 0

Views: 945

Answers (1)

cybersam
cybersam

Reputation: 66999

This query below looks similar to the one from @Lju. However, it has a few improvements.

  1. The MERGE for the Employer only needs to be done once, so it should come before the UNWIND. Otherwise, it would be done for every Employee.
  2. You should pass the employer name (or id) and the list of employee names (or ids) in parameters. In the following example, the Cypher code refers to the parameters as $employerName and $names.
  3. Also, since the WITH clause between the 2 MERGE clauses was just passing all identifiers forward, it is not needed. (However, Cypher syntax does require a WITH clause between a MERGE and an UNWIND).

Query:

MERGE (employer:Employer {name: $employerName})
WITH employer
UNWIND $names AS name
MERGE (employee:Employee {name: name})
MERGE (employer)-[:Employs]->(employee)
RETURN *

Upvotes: 1

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