I want to be able to update/enlarge my Neo4j database by uploading a newer version of that database OR part of that database.
Of what I've found I can use MERGE to add new nodes just if they don't already exists. But in that process, how do I in a slimmed way add new properties to that existing node if they don't exist?
I e, if I have a node 'John' of 'Age:34' and 'Hair:brown' and upload 'John'/'Age:34'/'Coat:Yellow' - how do I get 'John'/'Age:34'/'Hair:brown'/'Coat:Yellow'.
You could merge the node on John (or the primary identifying attribute). And then set the properties after the successful merge.
You could set them all at once with a map for all attributes
MERGE (n:Node {name: 'John'})
SET n = {name: 'John', age: 34, coat: 'Yellow', hair: 'Brown'}
RETURN n
If you just wanted to replace the attributes age and coat, you could do this instead.
MERGE (n:Node {name: 'John'})
SET n.age = 34, n.coat = 'Yellow'
RETURN n
Or you could add it as a map too
MERGE (n:Node {name: 'John'})
SET n += {age: 34, coat: 'Yellow'}
RETURN n
MERGE guarantees that a node will exist afterwards (either matched or created). If you don't want to create the node, you need to use MATCH instead. (Since you say "if node exists", that implies it shouldn't be created)
The simplest way is
MATCH (n{id:{uuid}) SET n.prop=true
If the match fails, their will be nothing to do the SET against.
Assuming that you would like to still have rows after; (for a more complex query) You can just make the match optional
...
OPTIONAL MATCH (n{id:{uuid}) SET n.prop=true
Again, if the match fails, n will be null, and the SET will do nothing
