apoc.rel.startNode

Details
Syntax	`apoc.rel.startNode(rel)`
Description	Returns the start `NODE` for the given virtual `RELATIONSHIP`.
Arguments	Name	Type	Description
	`rel`	`RELATIONSHIP`	The relationship to get the start node from.
Returns	`NODE`

Usage Examples

The examples in this section are based on the following graph:

CREATE (s1:Student {name: 'Priya'})
CREATE (s2:Student {name: 'Joachim'})
CREATE (s3:Student {name: 'Dominic'})
CREATE (s4:Student {name: 'Amir'})
CREATE (s5:Student {name: 'Natasha'})
CREATE (s6:Student {name: 'Elena'})

CREATE (t1:TestScore {score: 87})
CREATE (t2:TestScore {score: 90})
CREATE (t3:TestScore {score: 78})
CREATE (t4:TestScore {score: 84})
CREATE (t5:TestScore {score: 76})
CREATE (t6:TestScore {score: 92})

CREATE (a:Level {level: 'beginner'})
CREATE (b:Level {level: 'intermediate'})
CREATE (c:Level {level: 'advanced'})

MERGE (s1)-[:HAS]->(t1)-[:ASSIGNED_TO]->(b)
MERGE (s2)-[:HAS]->(t2)-[:ASSIGNED_TO]->(c)
MERGE (s3)-[:HAS]->(t3)-[:ASSIGNED_TO]->(a)
MERGE (s4)-[:HAS]->(t4)-[:ASSIGNED_TO]->(b)
MERGE (s5)-[:HAS]->(t5)-[:ASSIGNED_TO]->(a)
MERGE (s6)-[:HAS]->(t6)-[:ASSIGNED_TO]->(c);

If we create virtual relationships between students to see which students have the same understanding level of class material, we can use apoc.rel.startNode to return the relationship id of those virtual relationships:

apoc.create.vRelationship Procedure

MATCH (s1:Student)-[:HAS]->(:TestScore)-[:ASSIGNED_TO]->(l:Level)<-[:ASSIGNED_TO]-(:TestScore)<-[:HAS]-(s2:Student)
CALL apoc.create.vRelationship(s1,'SIMILAR_LEVEL',{level: l.level},s2)
YIELD rel
RETURN apoc.rel.startNode(rel) AS startNode;

Results
startNode
(:Student {name: "Priya"})
(:Student {name: "Joachim"})
(:Student {name: "Dominic"})
(:Student {name: "Amir"})
(:Student {name: "Natasha"})
(:Student {name: "Elena"})