Neo4j display only one node for 1 to many relationship - neo4j

i'm trying to solve a problem of the 1: many relationship display in neo4j. My dataset is as below
child,desc,type,parent
1,PGD,Exchange,0
2,MSE 1,MSE,1
3,MSE 2,MSE,1
4,MSE 3,MSE,1
5,MSE 4,MSE,1
6,BRAS 1,BRAS,2
6,BRAS 1,BRAS,3
7,BRAS 2,BRAS,4
7,BRAS 2,BRAS,5
10,NPE 1,NPE,6
11,NPE 2,NPE,7
12,OLT,OLT,10
12,OLT,OLT,11
13,FDC,FDC,12
14,FDP,FDP,13
15,Cust 1,Customer,14
16,Cust 2,Customer,14
17,Cust 3,Customer,14
LOAD CSV WITH HEADERS FROM 'file:///FTTH_sample.csv' AS line
CREATE(:ftthsample
{child_id:line.child,
desc:line.desc,
type:line.type,
parent_id:line.parent});
//Relations
match (child:ftthsample),(parent:ftthsample)
where child.child_id=parent.parent_id
create (child)-[:test]->(parent)
//Query:
MATCH (child)-[childrel:test*]-(elem)-[parentrel:test*]->(parent)
WHERE elem.desc='FDP'
RETURN child,childrel,elem,parentrel
It returns a display as below.
I want the duplicate nodes to be displayed as one. Newbie with Neo4J. Can anyone of the experts help please?

This seems like an error in your graph creation query. You have a few lines in your query specifying the same node multiple times, but with multiple parents:
6,BRAS 1,BRAS,2
6,BRAS 1,BRAS,3
I'm guessing you actually want this to be a single node, with parent relationships to nodes with the given parent ids, instead of two separate nodes.
Let's adjust your import query. Instead of using a CREATE on each line, we'll use MERGE, and just on the child_id, which seems to be your primary key (maybe consider just using id instead, as a node can have an id on its own, without having to consider the context of whether it's a parent or child). We can use the ON CREATE clause after MERGE to add in the remaining properties only if the MERGE resulted in node creation (instead of matching to an existing node.
That will ensure we only have one node created per child_id.
Rather than having to rematch the child, we can use the child node we just created, match on the parent, and create the relationship.
LOAD CSV WITH HEADERS FROM 'file:///FTTH_sample.csv' AS line
MERGE(child:ftthsample {child_id:line.child})
ON CREATE SET
child.desc = line.desc,
child.type = line.type
WITH child, line.parent as parentId
MATCH (parent:ftthsample)
WHERE parent.child_id = parentId
MERGE (child)-[:test]->(parent)
Note that we haven't added line.parent as a property. It's not needed, since we only use that to create relationships, and after the relationships are there, we won't need those again.

Related

Correct order of operations in neo4j - LOAD, MERGE, MATCH, WITH, SET

I am loading simple csv data into neo4j. The data is simple as follows :-
uniqueId compound value category
ACT12_M_609 mesulfen 21 carbon
ACT12_M_609 MNAF 23 carbon
ACT12_M_609 nifluridide 20 suphate
ACT12_M_609 sulfur 23 carbon
I am loading the data from the URL using the following query -
LOAD CSV WITH HEADERS
FROM "url"
AS row
MERGE( t: Transaction { transactionId: row.uniqueId })
MERGE(c:Compound {name: row.compound})
MERGE (t)-[r:CONTAINS]->(c)
ON CREATE SET c.category= row.category
ON CREATE SET r.price =row.value
Next I do the aggregation to count total orders for a compound and create property for a node in the following way -
MATCH (c:Compound) <-[:CONTAINS]- (t:Transaction)
with c.name as name, count( distinct t.transactionId) as ord
set c.orders = ord
So far so good. I can accomplish what I want but I have the following 2 questions -
How can I create the orders property for compound node in the first step itself? .i.e. when I am loading the data I would like to perform the aggregation straight away.
For a compound node I am also setting the property for category. Theoretically, it can also be modelled as category -contains-> compound by creating Categorynode. But what advantage will I have if I do it? Because I can execute the queries and get the expected output without creating this additional node.
Thank you for your answer.
I don't think that's possible, LOAD CSV goes over one row at a time, so at row 1, it doesn't know how many more rows will follow.
I guess you could create virtual nodes and relationships, aggregate those and then use those to create the real nodes, but that would be way more complicated. Virtual Nodes/Rels
That depends on the questions/queries you want to ask.
A graph database is optimised for following relationships, so if you often do a query where the category is a criteria (e.g. MATCH (c: Category {category_id: 12})-[r]-(:Compound) ), it might be more performant to create a label for it.
If you just want to get the category in the results (e.g. RETURN compound.category), then it's fine as a property.

Skip existing node while loading csv

i m new at neo4j and i d like to upload a csv file and create a set of nodes. However i have already some existing nodes that may exist on that csv file. Is there an option to load the csv, create the nodes based on each row and in case the node already exists skip that row?
Thanks
You can use the MERGE clause to avoid creating duplicate nodes and relationships.
However, you need to carefully read the documentation to understand how to use MERGE, as incorrect usage can cause the unintentional creation of nodes and relationships.
Merge will give you what you want, however you must be careful how you identify the record uniquely to prevent creating duplicates
I'll put the desired final form first as attention spans seem to be on the decline...
// This one is safe assuming name is a true unique identifier of your Friends
// and that their favorite colors and foods may change over time
LOAD CSV FROM 'data/friends.csv' AS line
MERGE (f:Friend { name: line[0]})
set a.favorite_food = line[1]
set a.favorite_color = line[2]
The merge above will create or find the Friend node with that matching name and then, regardless of whether we are creating it or updating it, set the attributes on it.
If we were to instead provide all the attributes in the merge as such:
// This one is dangerous - all attributes must match in order
// to find the existing Friend node
LOAD CSV FROM 'data/friends.csv' AS line
MERGE (f:Friend { name: line[0], favorite_food: line[1], favorite_color: line[2]})
Then we would fail to find an existing friend everytime their favorite_food or favorite_color was updated in our data being (re)loaded.
Here's an example for anyone who's imagination hasn't fully filled in the blanks...
//Last month's file contained:
Bob Marley,Hemp Seeds,Green
//This month's file contained:
Bob Marley,Soylent Green,Rainbow

Create doesn't make all nodes and relationships appear

I just downloaded and installed Neo4J. Now I'm working with a simple csv that is looking like that:
So first I'm using this to merge the nodes for that file:
LOAD CSV WITH HEADERS FROM 'file:///Athletes.csv' AS line
MERGE(Rank:rank{rang: line.Rank})
MERGE(Name:name{nom: line.Name})
MERGE(Sport:sport{sport: line.Sport})
MERGE(Nation:nation{pays: line.Nation})
MERGE(Gender: gender{genre: line.Gender})
MERGE(BirthDate:birthDate{dateDeNaissance: line.BirthDate})
MERGE(BirthPlace: birthplace{lieuDeNaissance: line.BirthPlace})
MERGE(Height: height{taille: line.Height})
MERGE(Pay: pay{salaire: line.Pay})
and this to create some constraint for that file:
CREATE CONSTRAINT ON(name:Name) ASSERT name.nom IS UNIQUE
CREATE CONSTRAINT ON(rank:Rank) ASSERT rank.rang IS UNIQUE
Then I want to display to which country the athletes live to. For that I use:
Create(name)-[:WORK_AT]->(nation)
But I have have that appear:
I would like to know why I have that please.
I thank in advance anyone that takes time to help me.
Several issues come to mind:
If your CREATE clause is part of your first query: since the CREATE clause uses the variable names name and nation, and your MERGE clauses use Name and Nation (which have different casing) -- the CREATE clause would just create new nodes instead of using the Name and Nation nodes.
If your CREATE clause is NOT part of your first query: your CREATE clause would just create new nodes (since variable names, even assuming they had the same casing, are local to a query and are not stored in the DB).
Solution: You can add this clause to the end of the first query:
CREATE (Name)-[:WORK_AT]->(Nation)
Yes, Agree with #cybersam, it's the case sensitive issue of 'name' and 'nation' variables.
My suggesttion:
MERGE (Name)-[:WORK_AT]->(Nation)
I see that you're using MERGE for nodes, so just in case any values of Name or Nation duplicated, you should use MERGE instead of CREATE.

Creating a relationship with an atribute - Neo4j

I'm learning about neo4j and I have the following question.
I have two groups of nodes, the first one is called Workers who have an ID and the name of the worker.
On the other hand there is another group of nodes, called products, which apart from the id, has the following attributes; price, name.
I want to make a relationship called "manipulate" where I relate a worker to the product that he is going to manipulate.
For this I have a trabajaensector.csv file which relates the workers by id, along with the products they are going to manipulate, also by id.
This is its form:
id1,id2,sector
1,1,fruteria
2,2,fruteria
3,2,fruteria
4,7,panaderia
5,5,fruteria
6,5,fruteria
7,9,bebidas
8,9,bebidas
9,10,bebidas
10,10,bebidas
11,3,pescaderia
12,8,panaderia
13,7,panaderia
14,9,bebidas
15,10,bebidas
16,4,pescaderia
17,2,fruteria
18,4,pescaderia
In summary, id1 (worker) manipulates id2 (product) and its sector is "fruteria/pescaderia/panaderia o bebida"
This is my CQL for creating manipulate relationship:
LOAD CSV WITH HEADERS FROM "file:///trabajaensector.csv" AS csvLine
MATCH(w:Worker),(p:Product) where w.id= toInt(csvLine.id1) and p.id=
toInt(csvLine.id2) create (w)-[sect:trabajasec]->(p) return sect
Here is my problem, the relationship is apparently creating well, however I am losing that third "sector" data, which indicates the sector where the worker works by manipulating that product.
For example, the relationship for a worker named Juan who manipulates apples should have in the relation the variable / attribute "fruteria" or for fish "pescaderia".
Any idea of how to properly include that data in the relationship and how to recover it?
You can add a sector property to the trabajasec relationships:
LOAD CSV WITH HEADERS FROM "file:///trabajaensector.csv" AS csvLine
MATCH (w:Worker), (p:Product)
WHERE w.id = TOINT(csvLine.id1) AND p.id = TOINT(csvLine.id2)
CREATE (w)-[sect:trabajasec {sector: csvLine.sector}]->(p)
RETURN sect;
To use the above query, you should first delete the trabajasec relationships created by your earlier LOAD CSV query.

CREATE UNIQUE with labels and properties

I'm using Neo4j 2.0.0-M06. Just learning Cypher and reading the docs. In my mind this query would work, but I should be so lucky...
I'm importing tweets to a mysql-database, and from there importing them to neo4j. If a tweet is already existing in the Neo4j database, it should be updated.
My query:
MATCH (y:Tweet:Socialmedia) WHERE
HAS (y.tweet_id) AND y.tweet_id = '123'
CREATE UNIQUE (n:Tweet:Socialmedia {
body : 'This is a tweet', tweet_id : '123', tweet_userid : '321', tweet_username : 'example'
} )
Neo4j says: This pattern is not supported for CREATE UNIQUE
The database is currently empty on nodes with the matching labels, so there are no tweets what so ever in the Neo4j database.
What is the correct query?
You want to use MERGE for this query, along with a unique constraint.
CREATE CONSTRAINT on (t:Tweet) ASSERT t.tweet_id IS UNIQUE;
MERGE (t:Tweet {tweet_id:'123'})
ON CREATE
SET t:SocialMedia,
t.body = 'This is a tweet',
t.tweet_userid = '321',
t.tweet_username = 'example';
This will use an index to lookup the tweet by id, and do nothing if the tweet exists, otherwise it will set those properties.
I would like to point that one can use a combination of
CREATE CONSTRAINT and then a normal
CREATE (without UNIQUE)
This is for cases where one expects a unique node and wants to throw an exception if the node unexpectedly exists. (Far cheaper than looking for the node before creating it).
Also note that MERGE seems to take more CPU cycles than a CREATE. (It also takes more CPU cycles even if an exception is thrown)
An alternative scenario covering CREATE CONSTRAINT, CREATE and MERGE (though admittedly not the primary purpose of this post).

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