Neo4j Cypher to Yield groups of nodes based on CSV column value

Question

I am new to neo4j. I am working with Neo4j Enterprise 4.4.5 version. I am trying to import a csv into neo4j and generate the nodes and relationships. I have a CSV with column headers Class, Level, Title and Relationship. Each row of the csv provides information of any individual node which I can use to create my nodes. The various relationships are, say, A, B, C and D. I would like to create groups of nodes, based on Relationship column value. As a result, I would yield 4 groups, set_A, set_B, set_C, set_D. Additionally, my node label would be dynamic and has multilabels. eg: [Class, Level]; I used apoc.merge.node() for this purpose.

The following is the query I wrote:

LOAD CSV WITH HEADERS FROM "file:///ABCD.csv" AS IsKg
WITH IsKg

WITH * WHERE (IsKg.Class <> "" OR IsKg.Level <> "") AND IsKg.Relationship = "A"
CALL apoc.merge.node(
    [IsKg.Class, IsKg.Level],
    {title:coalesce(IsKg.Title,"Unknown")}
)
YIELD node as set_A

WITH * WHERE (IsKg.Class <> "" OR IsKg.Level <> "") AND IsKg.Relationship = "B"
CALL apoc.merge.node(
    [IsKg.Class, IsKg.Level],
    {title:coalesce(IsKg.Title,"Unknown")}
)
YIELD node as set_B

The above query only created set_A nodes, not set_B.

The above query works fine, without the IsKg.Relationship conditions. From this I would deduce that, when I include an extra condition based on relationship, then the entire IsKg is not available to yield next set of nodes. Hence, set_B is not created. I would require to create 4 such groups. The purpose for creating my groups of nodes is to create relationships between them based on further criteria from another column called Hierarchy.

Any guidance on how I could make the above query work is much appreciated.

Thank you

Answer 1

I think you can group the nodes after the merge this way:

LOAD CSV WITH HEADERS FROM "file:///ABCD.csv" AS IsKg
WITH IsKg

WITH * WHERE (IsKg.Class <> "" OR IsKg.Level <> "") 
CALL apoc.merge.node(
    [IsKg.Class, IsKg.Level],
    {title:coalesce(IsKg.Title,"Unknown")}
)
YIELD node 
RETURN IsKg.Relationship AS IsKgRel, COLLECT(node) AS nodes

which should (not tested) return collections of nodes, one for each value of IsKg.Relationship