I am using a graph database having many nodes connected to a super node by a relationship TYPE. And each of those sub nodes have properties via a FROM relationship.
How should i access the properties of individual nodes in cypher query?
I tried this but its not working.
start a=node(2) match (a)<-[:TYPE]-(node) match (node)<-[:FROM]-(prop) where prop.name="ABC" return node;
Here i have to return a node with a property name whose value is ABC!?
How should i correct it?
START a=node(2)
MATCH (a)<-[:TYPE]-(node)<-[:FROM]-(prop)
WHERE prop.name="ABC"
RETURN node;
You could also do this using indexes:
START a=node:properties('name:ABC')
MATCH (node)<-[:FROM]-(a)
Where 'properties' is your index which indexes name as 'ABC'. Realize that your above query is only interested in the node related with :FROM, therefore searching in the first example could be very long compared to simply using indexing.
If you are using Neo4j 2.x, then you are far better off with labels.
MATCH (a:Property(name='ABC'))-[:FROM]->(node)
RETURN node
Where you would set the label 'Property' when you create/update a property node.
Related
I want to find all those nodes that are connected to specific node based upon certain relationship label. This is what I have got so far,
Match (n:UMLSConcepts{ConceptID: 'C3254924'})-[:NDFRT {RelationLabel : "RO_may_be_treated_by"}]-> (m:UMLSConcepts) RETURN (n), (m)
where (n) is a specific node and (m) are all other nodes that are connected with this node. Problem with above statement is that it is dependent upon a specific relation type in this case(NDFRT), but I want all relation type that contains certain relationship properties in this case("RO_may_be_treated_by") because there could be path/edge in other relation type as well.
If I I fully understood your question, you can simply omit the relationship type in your Cypher query, this way:
Match (n:UMLSConcepts{ConceptID: 'C3254924'})-[{RelationLabel : "RO_may_be_treated_by"}]-> (m:UMLSConcepts)
RETURN (n), (m)
Will Neo4j auto-generate unique ids for all the nodes created using 'CREATE' query, as 'id' in Mysql? We created a node with
CREATE (n: user{name:"x", age:10}) return n
If we want to update 'name' property, how to do it in Neo4j?
From the documentation though,
Searching for nodes by id can be done with the id() function in a predicate.
Neo4j reuses its internal ids when nodes and relationships are deleted. This means that applications using, and relying on internal Neo4j ids, are brittle or at risk of making mistakes. It is therefor recommended to rather use application generated ids.
It is a good idea to as they say, use Application generated ids that are stored as properties of the node. You need to set the application generated id while creating the node and then use that key on merge statements
MERGE (n:user{key:<myApplicationKey>}) return n
SET n.name="x", age=10
There is an internal id, you can access it the id() function
CREATE (n:User {name="x", age: 10}) RETURN n, id(n) as nodeId
Later on, you can update it with
MATCH (n) WHERE id(n) = 12345 SET n.name = "y"
In each of my nodes I have a selection of properties like education_id , work_id, locale etc etc. All these properties can have one or more than one values of the sort of education_id:112 or education_id:165 i.e. Node A might have education_id:112 and Node B might have education_id:165 and again Node C might have education_id:112 and so on.
I want a cypher query that return all nodes for a particular value of the property and I don't care about the value of the property beforehand.
To put it into perspective, in the example I have provided, it must return Node A and Node C under education_id:112 and Node B under education_id:165
Note: I am not providing multiple cypher queries specifying the values of properties each time. The whole output must be dynamic.
The output to the query should be something like
education_id:112 Node A, Node C
education_id:165 Node B
These are the results of a single query statement.
Not quite sure I understand your question, but based on the expected output:
MATCH (n) RETURN n.education_id,collect(n)
will group nodes by distinct values of education_id
You should probably take a look at the cypher refcard. What you are looking for is the WHEREclause:
Match (a) WHERE a.education_id = 112 return a
You can also specify property directly in the MATCH clause.
Match (a{education_id: 112}) RETURN a
My problem is really a basic example of using labels in Neo4j 2.0.M5. I try to drop all nodes and relationships, then I drop old 'Person' index, then I create a new 'Person' index based on 'name' property, then I create a node labeled 'Person' with name 'John Doe', to finally retrieve this node.
Cypher:
START n=node(*) MATCH n-[r?]-m WITH n, r DELETE n, r
DROP INDEX ON :Person(name)
CREATE INDEX ON :Person(name)
CREATE (n:Person {name:'Jhon Doe'})
start n=node:Person(name='Jhon Doe') return n
All works well, except at the end, when I try to retrieve my node. Neo4j throws an error :
Index `Person` does not exist
I try without creating the index, but it also doesn't work.
It's a really simple case, do you see the problem ?
For Neo4j 2.0, start is no longer necessary, and your query can be expressed as:
match (n:Person)
where n.name='Jhon Doe'
return n;
With the start syntax, you're specifying an index name. With v2.0, when creating an index based on a label, I don't believe the index can be referenced by name (as it's never been given a name; you've just told Neo4j to index nodes with the label Person based on the property name). Since there's no index called Person, this is probably why you're seeing that error.
I am using neo4j, I have nodes with two properties: name and id. I have an index on id.
I have relationships "CALL" with a property: "by_test". This property can take different value (id of any node).
Two nodes can have multiple CALL relationships with different by_test property value.
So let's say I have 1..N nodes linked by the same CALL.by_test property value.
Node1 -> Node2 -> Node3 -> .. -> Node N
How can I get all these nodes?
Do I need to put an Index on the relationship?
Do I have to create dynamic relationship? Instead of CALL.by_test=value, use value has a relationship.
Thanks!
Using Cypher, you could query for that list like this:
START n=node:node_auto_index(name="one")
MATCH p=(n)-[r:CALL*1..]->(m)
WHERE ALL(x in r WHERE x.by_test = 3)
RETURN n,m
In the MATCH you bind a term r to the CALL relationships, which you then use in the WHERE clause to check the by_test property of each.
As Michael Hunger noted, the r is a collection of relationships, so the WHERE needs to use ALL to check each of the relationships.