Neo4j - Load CSV and chain relationship

1
votes

I want to load a csv, a timeline of ordered events to create a list of nodes but I'm having trouble creating a :Next relationship to link two rows. 

LOAD CSV WITH HEADERS FROM "file:////events.csv" AS row
merge (:Event{id:row.id})-[:NEXT]-> ??? (:Event {id:row[+1].id)

I suppose one approach is to have a column in the CSV pointing to the next row id.

1
neo4jcypher

1 Answers

0
votes

The following queries assume the nodes already exist. If you also want to create the nodes as necessary, replace MATCH with MERGE.

Option 1:

You can have each row in the CSV file contain a variable number of node ids for the nodes that need to be connected together in a single chain, in order. In this case, the CSV file should not have a header row.

LOAD CSV FROM "file:///events.csv" AS ids
UNWIND [i IN RANGE(1, SIZE(ids)-1) | {a: ids[i-1], b: ids[i]}] AS pair
MATCH (a:Event {id: pair.a})
MATCH (b:Event {id: pair.b})
MERGE (a)-[:NEXT]->(b)

Option 2:

You can have each row in the CSV file contain just a pair of node ids that need to be connected together, in order. In this case, the CSV file could have a header row, as demonstrated by this example (using a and b as the headers).

LOAD CSV WITH HEADERS FROM "file:///events.csv" AS pair
MATCH (a:Event {id: pair.a})
MATCH (b:Event {id: pair.b})
MERGE (a)-[:NEXT]->(b)