Say I have a graph with people who can know each other and do crime. Now I want to get all the criminals who know each other. So I do something like this:
MATCH (c:Crime)<-[:PARTY_TO]-(p1:Person)<-[:KNOWS]-(p2:Person)-[:PARTY_TO]->(c2:Crime)
Now the question is: does this cypher return two different persons who have commited the same crime?
I know that if I did:
MATCH (c:Crime)<-[:PARTY_TO]-(p1:Person)<-[:KNOWS]-(p2:Person)-[:PARTY_TO]->(c:Crime)
Then they would have commited the same crime, but if the two crimes have a different label, can they be the same?
You use the same label :Crime so it is the same crime. If the crime has another label and you use it on your query then it should be fine.
For example; you have a name and a nickname; if your friend calls you
by your nickname (another label); then you are still the same person
when another person calls you by your real name.
Nodes can be labelled more than once (like :Crime and :Robbery) but it is referring to the same node.
Related
I have the following graph:
I would look to get all contractors and subcontractors and clients, starting from David.
So I thought of a query likes this:
MATCH (a:contractor)-[*0..1]->(b)-[w:works_for]->(c:client) return a,b,c
This would return:
(0:contractor {name:"David"}) (0:contractor {name:"David"}) (56:client {name:"Sarah"})
(0:contractor {name:"David"}) (1:subcontractor {name:"John"}) (56:client {name:"Sarah"})
Which returns the desired result. The issue here is performance.
If the DB contains millions of records and I leave (b) without a label, the query will take forever. If I add a label to (b) such as (b:subcontractor) I won't hit millions of rows but I will only get results with subcontractors:
(0:contractor {name:"David"}) (1:subcontractor {name:"John"}) (56:client {name:"Sarah"})
Is there a more efficient way to do this?
link to graph example: https://console.neo4j.org/r/pry01l
There are some things to consider with your query.
The relationship type is not specified- is it the case that the only relationships from contractor nodes are works_for and hired? If not, you should constrain the relationship types being matched in your query. For example
MATCH (a:contractor)-[:works_for|:hired*0..1]->(b)-[w:works_for]->(c:client)
RETURN a,b,c
The fact that (b) is unlabelled does not mean that every node in the graph will be matched. It will be reached either as a result of traversing the works_for or hired relationships if specified, or any relationship from :contractor, or via the works_for relationship.
If you do want to label it, and you have a hierarchy of types, you can assign multiple labels to nodes and just use the most general one in your query. For example, you could have a label such as ExternalStaff as the generic label, and then further add Contractor or SubContractor to distinguish individual nodes. Then you can do something like
MATCH (a:contractor)-[:works_for|:hired*0..1]->(b:ExternalStaff)-[w:works_for]->(c:client)
RETURN a,b,c
Depends really on your use cases.
I'm doing an experiment with using a graph database (neo4j). I have two csv's that I imported into a neo4j datastore. I'm a little shakey on the neo terminology; so forgive me. Lets say I have:
Customer (AccountNumber, CustomerName) and
CustomerGroups (AccountNumber, GroupName).
I would like to create a new Node called groups which is comprised of the distinct GroupName from CustomerGroups. I'll call it Group.
I then want to create relationships "HAS_GROUP" from Customer to Group using the common AccountNumber from CustomerGroups.
Once the above is completed, I could delete CustomerGroups as its no longer needed.
I'm just stuck at the syntax. I can get the distinct groups from CustomerGroups with:
MATCH (n:CustomerGroups) distinct n.GROUP_NAME
and I get back about 50 distinct groups, but can't figure how to add the create statement to the results and CREATE g:Group {GroupName: n.GROUP_NAME}
I then know my followup question is how to do the MATCH to the new group using the old table with common account numbers.
FYI: I've indexed the AccountNumber in both Nodes. Both Customer and CustomerGroups have over 5 Million nodes. Not bad for a laptop (2 min to import using neo4j-import). I was impressed!
Thanks for any help you can give!
Instead of creating a CustomerGroups label and creating nodes for that, you should be able to define relationships that you would like to create in your neo4j-import. It would certainly be a lot faster too. See:
http://neo4j.com/docs/stable/import-tool-header-format.html
To your question, you could probably do something like:
MATCH (cg:CustomerGroup)
MATCH (customer:Customer {AccountNumber: cg. AccountNumber}), (group:Group {GroupName: cg.GroupName})
CREATE (customer)-[:IN_GROUP]->(group)
You'd definitely want to make sure you have indexes on :Customer(AccountNumber) and :Group(GroupName) first. But even then it would still be much slower than doing it as part of your initial import.
Also, you may or may not want MERGE instead of CREATE
I have read the Neo4j manual and saw the numerous short examples regarding movie graph. I have also installed it locally and played with the cypher.
Here is the setup:
I have the following nodes: Movies (with name and id, owned by friend), Actors(with name and ids) Directors (with names and id), Genre (with id and name)
Relations are: Actors acted in Movies (1 movie - many actors), Directors directed a movie (1 director per movie but a director can direct many movies), and Movies has several genre "(many to many)
1) Owned by friend I dont know why but following the LOAD CSV example they put USA as a node rather than a property but is there a logical reason why its better to put it as a node rather than a property like i did?
2)
What I want to search is similar to the answer given to this question:
Nearest nodes to a give node, assigning dynamically weight to relationship types
However - I do not have a weight on the relationship and its more of a "go find the first give nodes connected to it"
Given that the "owned by friend" can only be owned by 1 person.
If given movie title "Spider-Man" (which for example purpose is owned by frank) go find the next occurrence of a movie that is owned by John.
So after reading Neo4j I believe that I dont need to specify which relationship is needed to traverse but just go find the next movie that meets my criteria, right?
So Following the above link
MATCH (n:Start { title: 'Spider-Man' }),
(n)-[:CONNECTED*0..2]-(x)
RETURN x
So go to node Spider-Man and go find me X as long as it is connected but I got stump by *0..2 because its the range...what if I just say "go find me the first you that means the own by John"
3) following up to #2 - how do i insert the fitler "own by john" ?
There are a number of things in your question that don't quite make sense. Here's a stab at an answer.
1) Making 'USA' a node rather than a property is useful if you want to search based on country. If 'USA' is a node, you are able to limit your search by starting at the 'USA' node. If you don't care to do this, then it doesn't really matter. It may also save a small amount of space for longer country names to store the name once and link to it via relationships.
2) Your example doesn't match your described graph. I can't really speak to it without a better example.
3) This is probably easy to answer once you improve your example.
OK. Based on the comments to the answer, here's what you need. To find one movie owned by John that is connected via common actors, directors, etc to the movie Spider-man owned by Frank (that is, sub-graphs like (movie)<--(actor)-->(movie) ) you can write:
MATCH (n:Movie {title : 'Spider-Man', owned_by : 'Frank'})<-[*2]->(m:Movie {owned_by : 'John'})
RETURN m LIMIT 1
If you want more responses, alter or remove the LIMIT on the RETURN clause. If you want to allow chains that pass through chains like (movie)<--(actor)-->(movie)<--(director)-->(movie), you can increase the number of relationships matched (the *2) to 4, 6, 8, etc. You probably shouldn't just write the relationship part of the MATCH clause as -[*]-, because this could get into infinite loops.
I'm using ne04j 2.1.2 community edition.
I have a nodes with a label called Company and I created these nodes and label by loading CSV file along with the MERGE and CREATE commands.
So in future if my label names changes,say Company to Organization, I wanted to maintain the createddate, UpdatedDate, NewLabelName, OldLabelName values somewhere.
So in order to achieve that I thought of maintaining one master node which holds the label information i.e., it should have the properties like NewLabelName, OldLabelName, CreatedDate, UpdatedDate. So the label name should come from the Master Node to other nodes. Whenever we made any changes to label ,then the corresponding UpdatedDate property value should be updated in the master node and NewLabelName should come from the master node to other nodes (nodes for which that label belongs to) .
Hope you understand the scenario here.
But how can i achieve this ? is it possible to achieve ? if yes, then how can i define the relationship between master and other nodes?
(Here my other nodes are Name of the Companies like Google, Yahoo, Samsung etc.. and those will be having some other child nodes like location)
Please suggest the solution. (I wanted to achieve these using cypher not using java)
Thanks
Although labels can be changed, you should do that rarely (e.g., to recover from a mistake). Changing a large number of labels is very expensive and should never be done as a part of normal processing.
Also, like a Java class name, a label name is not something you'd normally show to end users. So, there is really no reason to ever change them. Just try to pick reasonable label names to start with, and don't plan to change them.
My graph is composed of multiple "sub-graphes" that are disconnected from one another. These sub-graphes are composed of nodes that are connected with a given relation type.
I would like to get (for example) the list of sub-graphes that contain at least one node that has the property "name" equals "John".
It's equivalent to finding one node per subgraph having this property.
One solution would be to find all the nodes having this property and loop through this list to only pick the ones that are not connected to the previously picked ones. But that would be ugly and quite heavy. Is there an elegant way to do that with Cypher?
I'm trying with something along this direction but have no success so far:
START source=node:user('name:"John"')
MATCH source-[r?:KNOWS*]-target
WHERE r is null
RETURN source
Try this one it may help
START source=node:user('name:"John"')
MATCH source-[r:KNOWS]-()-[r2:KNOWS]-target
WHERE NOT(source-[r:KNOWS]-target)
RETURN target