I have created graph using MERGE to avoid repetition, following is the query
LOAD CSV WITH HEADERS
FROM "file:///C:/Users/username/Desktop/file.csv"
AS network
MERGE (sourceNode {id:network.node1})
MERGE (destNode {id:network.node2})
WITH sourceNode,
destNode,
network
It doesn't assign labels to nodes but I need labels to query graph. Is there any way to assign labels to nodes?
Thanks in advance.
You seemed to miss the variables which are supposed to be assigned to a node before the labels.This way your nodes will be assigned labels and you can use their respective variables for operations on them. I've modified the query. Hope this helps!
LOAD CSV WITH HEADERS
FROM "file:///C:/Users/username/Desktop/file.csv"
AS network
MERGE (n:sourceNode {id:network.node1})
MERGE (m:destNode {id:network.node2})
WITH n,m,network
You may want to review the developer guide. Here's how to create a node with a label. However, if you want to set a label dynamically, such as from a CSV, then you will need to use APOC Procedures for this, as it is not supported natively by Cypher.
Related
I have created a nice graph using Neo4j Desktop, using a local CSV file that I added to the project. now I'm trying to use python to do that automatically for that I'm trying to use methods from here https://py2neo.org/2021.1/bulk/index.html like create/merge nodes/relatioships.
I have 2 questions,
Do I need to use create method (create node for exmaple) and after that to use merge method (merge nodes for this example) or can use merge nodes from the begining?
I have tried to use merge only and I got some wierd things when I'm using large sample size.
2)After creation of nodes and relationships how can I change the visualization of the nodes (put some value in the node)?
*If there is an other way to use python to create graph from a big CSV file I would like to hear, Thanks!
So I am planning to create a geohash Graph with neo4j.
my CSV contains ,for each row, two informations for geohash one for pickup and another for dropoff as follow :
What I want is:
the node that have the same geohash as another one shouldn't be recreated (so multiple edges are allowed).
one node could be a pickup and a dropoff in the same time
I tried to use MERGE but works by columns:
load csv from "file:///green_data.csv" as line
merge(pick:pickup{geohash:line[20]})merge (drop:dropoff{geohash: line[22]})merge(pick)-[:trip]->(drop)
as you can see , the same geohash dr5rkky node is being created twice one for pickups and another for dropoffs
how to avoid that ?
load csv from "file:///green_data.csv" as line MERGE(p:HashNode {geohash: line[20]}) ON CREATE set p.pickup=True ON MATCH set p.pickup=True MERGE(d:HashNode {geohash: line[22]}) ON CREATE set d.dropoff=True ON MATCH set d.dropoff=True MERGE (p)-[:trip]->(d)
Base on neo4j docs:
MERGE either matches existing nodes and binds them, or it creates new data and binds that. It’s like a combination of MATCH and CREATE that additionally allows you to specify what happens if the data was matched or created.
The last part of MERGE is the ON CREATE and ON MATCH. These allow a query to express additional changes to the properties of a node or relationship, depending on if the element was MATCH -ed in the database or if it was CREATE -ed.
In Neo4j, is there a way of enforcing that a node of a label X is not connected to a node of label Y?
For example, if someone tried to run a query such as:
MERGE (:X)-[:SOME_RELATIONSHIP]->(:Y)
would there be a way to guarantee that such a query would fail?
Thank you!
Neo4j's constraints don't currently support relationship existence or restriction, so you'd need to put in some extra work.
If you have APOC Procedures, you could register a trigger which could get evaluated to check if a relationship being created connects two nodes of those labels and use apoc.util.validate() to generate an error which will fail and rollback the transaction.
If you want to do this without APOC, it's a bit more work, as you'll need to create a TransactionEventHandler, and then a kernel extension to load your event handler. Here's a blog entry on this approach.
I have imported a csv file into neo4j. I have been trying to define a large number of properties (all the columns) for each node. How can i do that without having to type in each name?
I have been trying this:
USING PERIODIC COMMIT
load csv WITH headers from "file:///frozen_catalog.csv" AS line
//Creating nodes for each product id with its properties
CREATE (product:product{id : line.`o_prd`,
Gross_Price_Average: TOINT(line.`Gross_Price_Average`),
O_PRD_SPG: TOINT(line.`O_PRD_SPG`)});
You can adding properties from maps. For example:
LOAD CSV WITH HEADERS FROM "http://data.neo4j.com/northwind/products.csv" AS row
MERGE (P:Product {productID: row.productID})
SET P += row
http://neo4j.com/docs/developer-manual/current/cypher/clauses/set/#set-adding-properties-from-maps
The LOAD CSV command cannot perform automatic type conversion to ints on certain fields, that must be done explicitly (though you can avoid having to explicitly mention all other fields by using the map projection feature to transform your line data before setting it via stdob--'s suggestion).
You may want to take a look at Neo4j's import tool, as this will allow you to specify field type in headers, which should perform type conversion for you.
That said, 77 columns is a lot of data to all store on individual nodes. You may want to take another look at your data and figure out if some of those properties would be better modeled as nodes with their own label with relationships to your product nodes. You mentioned some of these were categorical properties. Categories are well suited to be modeled separately as nodes instead of as properties, and maybe some of your other properties would work better as nodes as well.
I have csv with header like :
string,alias,source
I was trying to use query like this :
USING PERIODIC COMMIT 1000 LOAD CSV WITH HEADERS FROM file AS line WITH line
Match (p{name:SUBSTRING(line.string ,7)})
Create (p:line.source:line.alias)
but I get error about last line. Is it possible to add new property to exsisting node using loadCsv ?
I think you're looking for the SET command. CREATE is reserved for nodes, relationships, and patterns.
You may want to review the documentation or the Cypher reference.
Also your match doesn't seem to be using a label (you're only using the variable p). If at all possible, use labels in your graph, without them you can't take advantage of your indexes or unique constraints, and even without those, it ensures that you're only scanning over nodes of that label instead of your entire graph.