return 1 node even in presence of duplicate nodes in neo4j

neo4j merge duplicate nodes
neo4j create node if not exists
neo4j match node by id
neo4j return path
neo4j query all nodes
neo4j collect
neo4j get all connected nodes
neo4j create relationship if not exists

Consider a node Person :

I need all nodes which are unique only i.e. even if two or more nodes with same properties exist (in this case it is nodes with name 'B') i need only one node among the duplicate nodes in my search statement (in this case only one 'B' node among the two is to be returned) which would be something like this MATCH (n:PERSON) WHERE [ n.name is unique ] RETURN n.name . Can i know what is the exact query for my requirement ?

I'm not realy sure what you are after. The Destinct will return B only once

MATCH (n :Person {name: 'B'})
RETURN DISTINCT n

Hope it helps

Exact match - Check for duplicate nodes / check , I am working to create a few cypher queries to check for previously encountered issues as new return sum(cpr-1) as numDuplicateNodes. Sometimes you only need to return a count of the results found in the database, rather than returning the objects themselves. The count() function in Cypher allows you to count the number of occurences of entities, relationships, or results returned.

If you're only looking for a single result, LIMIT should do the trick:

MATCH (n:Person{name:'B'})
RETURN n LIMIT 1

If you're looking up based on multiple rows, such as an input collection, then you only want a single result per row, so you can collect and take the first result:

UNWIND ['A','B','C'] as name
MATCH (n:Person {name:name})
WITH name, head(collect(n)) as n
RETURN n

If you have access to APOC Procedures you can also use APOC aggregation functions instead:

UNWIND ['A','B','C'] as name
MATCH (n:Person {name:name})
WITH name, apoc.agg.first(n) as n
RETURN n

3.15. MERGE - Chapter 3. Clauses, 3.15.1. Introduction. MERGE either matches existing nodes and binds them, or it For example, you can specify that the graph must contain a node for a user with a Note that even though the MATCH clause results in three bound nodes The query finds all the Person nodes, sets a property on them, and returns them. In Neo4j database, CQL CREATE command always creates a new node or relationship which means even though you use the same values, it inserts a new row. As per our application requirements for some nodes or relationships, we have to avoid this duplication. For this, we should use some database

The cypher equivalent of MATCH (n:PERSON) WHERE [ n.name is unique ] RETURN n.name would simply be MATCH (n:PERSON) RETURN DISTINCT n.name. RETURN DISTINCT filters out any duplicate row results. If you returned the node, RETURN DISTINCT would not work because the different internal node id's would make the 2 rows distinct from each other.

Now, assuming that you do want to return the nodes, but want to ignore their internal ID, you will need to do something like this...

MATCH (n) 
// Collect results into one list for filtering
WITH COLLECT(n) as ns 
RETURN FILTER(n IN ns 
  WHERE NONE(
    // Remove nodes that share all properties
    PROPERTIES(n)=PROPERTIES(x) AND
    // But keep 1 instance. In this case, the one with the lowest ID
    x in ns WHERE ID(x) < ID(n)
)) as ns

Beginning Neo4j, even more important when using constraints, as this needs to return 1 node, as it means you can create unique nodes, and if there's a problem, it'll error. them as needed, to help once again with reducing duplicates within the code. The MERGE clause ensures that a pattern exists in the graph. Either the pattern already exists, or it needs to be created. Merge single node with a label. Merge single node with properties. Merge single node specifying both label and property. Merge single node derived from an existing node property. Use ON CREATE and ON MATCH.

Understanding how MERGE works - Neo4j Graph Database , In this case, all of them; a new :Student node will be created with the given id, and a new Otherwise, duplicate nodes will be created, which might escape notice, To use the existing nodes and relationships in the graph, MATCH or MERGE on This is because even if the the :FOR_TERM relationship exists between theĀ  With Neo4j 3.1.3 and higher, and APOC Procedures 3.1.3.6 and higher, you can use use new path expander features to limit expansion to certain nodes. The limit param is only usable with path expander procedures that take a config map, and only when using the end node ( >) or termination label filters ( / ):

Common Confusions on Cypher (and How to Avoid Them), Cypher: Limiting the number of returned links for a selection of nodes We know there's already a :Person node in the graph with the Numbers 2 and 3 would be okay, but the query throws an error because number 1 violates the uniqueness constraint. Want to sharpen your Cypher even more? Expected result The following query should create exactly one relationship between the two nodes, even if executed concurrently by multiple threads: MATCH (n), (m) WHERE ID(n) = {id1} AND ID(m) = {id2} MERGE (n)-[r:TEST]->(m) Actual resu

Delete duplicate node checking if specific keys have same values , Delete duplicate node checking if specific keys have same values The Cypher query below walks through the list of nodes by name and uses YIELD node RETURN name, max(idx) + 1 AS `Nbr Nodes Merged`. OUTPUT (6 replies) Unique indexes are great to prevent duplicates being created but is there a suggested approach for identifying duplicates across the graph. E.g. with the movie graph if you don't implement unique indexes (because movies can have the same name) and two people create the same movie with the same actors is there a way to identify the duplication?