CREATE after OPTIONAL MATCH where no match was found

Question

I\'m trying to write a query that will create some relationships if another relationship already exists.

START a=node(1), b=node(2), c=node(3)
OPTIONAL MATC         


        

Answer 1

For now, you can work around this using FOREACH and CASE. For example:

START a=node(1), b=node(2), c=node(3)
OPTIONAL MATCH (a)-[r1:RELATIONSHIP]-(optional1)
OPTIONAL MATCH (b)-[r2:RELATIONSHIP]-(optional2)
FOREACH (o IN CASE WHEN optional1 IS NOT NULL THEN [optional1] ELSE [] END |
  CREATE (c)-[:NEW_RELATIONSHIP]->(optional1)
)
FOREACH (o IN CASE WHEN optional2 IS NOT NULL THEN [optional2] ELSE [] END |
  CREATE (c)-[:NEW_RELATIONSHIP]->(optional2)
)
DELETE r1, r2
RETURN a, b, c

I suspect this will be made simpler in future Cypher language updates.

PS. You probably shouldn't use START anymore, but I imagine you have simply for the convenience of an example.