Cypher - conditional where clause

Question

I am trying to update a users subject name either by id or by name. Currently the query I have is this:

 MATCH (s:Subject)-[:REGISTERED-BY]->(u:User{id: 1})
 WHERE s.name="Math" or s.id=""
 SET s.name = "Maths"
 RETURN s

If I only use the name without OR , it works. If I only use ID and leave name as an empty string it works. But if I use the name and leave id empty in the OR clause. The update doesn't happen I need to conditionally update the names, depending on whether the name is available or the id. The id field is a UUID. Is there a way to write that logic in the query itself?

Answer 1

This may help you, In Neo4j you can perform conditional operations using two options.

If you have access to APOC, then you can use APOC.do.when :

MATCH (s:Subject)-[:REGISTERED-BY]->(u:User{id: 1})

WHERE ...

CALL apoc.do.when(s.name="Math", "SET s.name = \"Maths\"", "", {}) YIELD value as _

RETURN s

The second is a more native FOREACH :

MATCH (s:Subject)-[:REGISTERED-BY]->(u:User{id: 1})

WHERE ...

FOREACH(_ IN CASE s.name WHEN "Math" THEN [1] ELSE [] END | SET s.name = "Maths" )

RETURN s