Set Property of a Realtionship to label in Neo4j - neo4j

I have a few Realtionships in Neo4J with the label "[r:Absatraction]". They all have a Property on them like "SysML:refine" or "SysML:trace" or "SysML:verify".
These "Abstractions connect differently labeled nodes. Now I want Neo4j to replace the Label "Abstraction" with the labels from the "SysML" Property. So that on the graph one can see "[r:refine],[r:verify]...".
I tried: apoc.create.addLabels, but it only seems to work for nodes.
Is there a way to do that?

In neo4j terminology, a relationship must have a single "type" -- not an optional set of "labels" (which are only for nodes). Furthermore, a relationship's type cannot be changed.
So, to do what you want, you'd have to create new relationships (with the desired types) and delete the old ones.
For example, here's is how you can use the APOC procedure apoc.create.relationship to create new relationships with the right types (and with the same properties as the old relationships except for SysML), and delete the old relationships:
MATCH (a:Foo)-[r:Abstraction]->(b:Foo)
CALL apoc.create.relationship(a, r.SysML, apoc.map.removeKey(PROPERTIES(r), 'SysML'), b) YIELD rel
DELETE r
RETURN rel

It is not possible to rename realtionships so one has to create a new one.
Example string for this problem:
match (a)-[old:Abstraction]->(b) where old.SysML = "Verify"
create (a)-[new:Verify]->(b)
delete old

Related

Is there a way a relationship is automatically created when the nodes are created, given that the labels of the nodes already exist?

I created two labels A and B with a relationship CONNECT. I need to create multiple nodes of of each label A and B and a relationship between them. i.e, for each node A and B, I need to create a relationship.
e.g.: a1:A -[:CONNECT]-> b1:B, a2:A -[:CONNECT]-> b2:B,a3:A -[:CONNECT]-> b3:B, ... an:A -[:CONNECT]-> bn:B
Is there a way to create the relationship automatically? When I create nodes, can the db automatically create a relationship between the
nodes of different existing labels? Please help.
I used the APOC procedure to create multiple relationships between nodes manually on a property - for 100 nodes of labels LABEL1 and LABEL2, on a property value, I can create a relationships manually with a single Cypher query using below proc:
MATCH (ref1:LABEL1), (ref2:LABEL2)
WHERE ref1.property = ref2.property
CALL apoc.create.relationship(ref1, ‘RELATIONSHIP_NAME', {}, ref2) YIELD rel
RETURN rel
But I want to know if a way exists, where a relationship between two labels A and B already exists; and whenever a new node of label A and B are created, a relationship automatically creates without running a cypher query.
If you want to create a relationship between 2 nodes created at the same time, just specify that pattern in your CREATE clause.
Here is example using LOAD CSV to import data:
LOAD CSV WITH HEADERS FROM 'file:///data.csv' AS row
CREATE (a:A {x: row.x})-[:CONNECT]->(b:B {y: row.y})
Generally, it would be risky for a DB to automatically create relationships on your behalf since it might cause relationships to be created that you did not intend.
[UPDATE]
However, if Label2 nodes are created at a later time than Label1 nodes, and you are sure you want to automatically create the CONNECT relationship, you can use APOC to create a trigger like this:
CALL apoc.trigger.add(
"create-CONNECT-rel",
"UNWIND $createdNodes AS ref2
WITH ref2
WHERE ref2:Label2
MATCH (ref1:Label1 {property: ref2.property})
CREATE (ref1)-[:CONNECT]->(ref2)",
{phase:'before'})

Create a relationship only if not exist in neo4j

I want to add a relationship between two nodes, but only if the relationship does not exist. For example:
The Relationship between node1 and node2 currently exists with these properties: time:41221323,link:www.google.com
I am trying to add a relationship with different properties for example:
time:5344241,link:www.google.com
In this case i want to keep the original properties on the relationship.
You can use the below CQL query:
MATCH(a: startNodeLabel {attributes to match start node})
MATCH(m:endNodeLabel {attributes to match end node})
MERGE(a)-[:relationshipName]->(m)
The above merge statement creates relation between nodes a and m if there is no existing relationship between a and m.
You want either the MERGE or CREATE UNIQUE clause:
http://neo4j.com/docs/stable/query-merge.html
http://neo4j.com/docs/stable/query-create-unique.html
Also note that MERGE comes with additional ON CREATE SET and ON MATCH SET so you can control when properties get set.
I believe if you give either specific properties as part of the match syntax it will not create only if all of the properties match exactly.
Create Unique clause does serve this purpose. Neo4j Documet says
CREATE UNIQUE is in the middle of MATCH and CREATE — it will match
what it can, and create what is missing. CREATE UNIQUE will always
make the least change possible to the graph — if it can use parts of
the existing graph, it will.
START a=node(...), b=node(...)
CREATE UNIQUE (a)-[r:LIKES]-(b)
return a,b;

How to create a relationship to existing nodes based on a condition of matching properties

In Neo4j, I am trying to load a CSV file whilst creating a relationship between nodes based on the condition that a certain property is matched.
My Cypher code is:
LOAD CSV WITH HEADERS FROM "file:C:/Users/George.Kyle/Simple/Simple scream v3.csv" AS
csvLine
MATCH (g:simplepages { page: csvLine.page}),(y:simplepages {pagekeyword: csvLine.keyword} )
MATCH (n:sensitiveskin)
WHERE g.keyword = n.keyword
CREATE (f)-[:_]->(n)
You can see I am trying to create a relationship between 'simplepages' and 'sensitiveskin' based on their keyword properties being the same.
The query is executing but relationships won't form.
What I hope for is that when I execute a query such as
MATCH (n:sensitiveskin) RETURN n LIMIT 25
You will see all nodes (both sensitive skin and simple pages) with auto-complete switched on.
CREATE (f)-[:_]->(n) is using an f variable that was not previously defined, so it is creating a new node (with no label or properties) instead, and then creating a relationship from that new node. I think you meant to use either g or y instead of f. (Probably y, since you don't otherwise use it?)

How to generate relationships using property information [Node4j]

I have imported a CSV where each Node contains 3 columns. id, parent_id, and title. This is a simple tree structure i had in mysql. Now i need to create the relationships between those nodes considering the parent_id data. So each node to node will have 2 relationships as parent and child. Im really new to node4j and suggestions ?
i tried following, but no luck
MATCH (b:Branch {id}), (bb:Branch {parent_id})
CREATE (b)-[:PARENT]->(bb)
It seems as though your cypher is very close. The first thing you are going to want to do is create an index on the id and parent_id properties for the label Branch.
CREATE INDEX ON :Branch(id)
CREATE INDEX ON :Branch(parent_id)
Once you have indexes created you want to match all of the nodes with the label Branch (I would limit this with a specific value to start to make sure you create exactly what you want) and for each find the corresponding parent by matching on your indexed attributes.
MATCH (b:Branch), (bb:Branch)
WHERE b.id = ???
AND b.parent_id = bb.id
CREATE (b)-[:PARENT]->(bb)
Once you have proved this out on one branch and you get the results you expect I would run it for more branches at once. You could still choose to do it in batches depending on the number of branches in your graph.
After you have created all of the :PARENT relationships you could optionally remove all of the parent_id properties.
MATCH (b:Branch)-[:PARENT]->(:Branch)
WHERE exists(b.parent_id)
REMOVE b.parent_id

Adding relationship to existing nodes with Cypher

I'm trying out Neo4j for the first time. I'm using the 2.0-RC1 community edition.
I've created some nodes:
MERGE (u:User{username:'admin',password:'admin'})
MERGE (r1:Role{name:'ROLE_ADMIN'})
MERGE (r2:Role{name:'ROLE_WEB_USER'})
MERGE (r3:Role{name:'ROLE_REST_USER'})
and now I want to add relationships between the nodes. However, I don't want to clear out the existing database created with the script above, add the statements and run it again. I want to add relationships to the existing nodes. Google helped me find this:
START n=node(*), m=node(*)
where has(n.username) and has(m.name) and n.username = 'admin'
and m.name = 'ROLE_WEB_USER'
create (n)-[:HAS_ROLE]->(m)
Which works fine (even though I don't understand all the syntax). However, I am aware that this finds any node with a username property and any node with a name property, instead of using labels to check that it has the right type of node.
How can I do the same using labels?
In Neo4j 2.0 you can create schema indexes for your labels and the properties you use for lookup:
CREATE INDEX ON :User(username)
CREATE INDEX ON :Role(name)
To create relationships you might use:
MATCH (u:User {username:'admin'}), (r:Role {name:'ROLE_WEB_USER'})
CREATE (u)-[:HAS_ROLE]->(r)
The MATCH will use an index if possible. If there is no index, it will lookup up all nodes carrying the label and see if the property matches.
N.B. the syntax above will only work with Neo4j 2.0.0-RC1 and above.
Update as of 4/2020:
The new Cypher syntax is as follows. as 'CREATE INDEX ON' has been deprecated is..
CREATE INDEX FOR (n:Label) ON (n.property)

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