Creating and Modifying Data

Now that you can read data with MATCH and WHERE, it is time to learn how to create, update, and delete data in Neo4j using Cypher.

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CREATE — Adding New Data

The CREATE clause adds new nodes and relationships to the graph:

Create a node

CREATE (p:Person {name: "Alice", age: 30})
RETURN p

Create multiple nodes

CREATE (a:Person {name: "Alice", age: 30})
CREATE (b:Person {name: "Bob", age: 25})
RETURN a, b

Create a relationship

MATCH (a:Person {name: "Alice"})
MATCH (b:Person {name: "Bob"})
CREATE (a)-[:FRIENDS_WITH {since: 2022}]->(b)

Create nodes and relationships together

CREATE (a:Person {name: "Alice"})-[:WORKS_AT {role: "Engineer"}]->(c:Company {name: "Acme"})
RETURN a, c

Important: CREATE always creates new data. If a node with the same properties already exists, it will create a duplicate.

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MERGE — Create If Not Exists

MERGE is the idempotent alternative to CREATE — it only creates data if it does not already exist:

Merge a node

MERGE (p:Person {name: "Alice"})
RETURN p

If a :Person node with name: "Alice" exists, it is returned. If not, it is created.

ON CREATE and ON MATCH

Execute different logic depending on whether the node was created or already existed:

MERGE (p:Person {name: "Alice"})
ON CREATE SET p.createdAt = datetime()
ON MATCH SET p.lastSeen = datetime()
RETURN p

Merge a relationship

MATCH (a:Person {name: "Alice"})
MATCH (b:Person {name: "Bob"})
MERGE (a)-[:FRIENDS_WITH]->(b)

Tip: Always MERGE on the minimum set of properties that uniquely identify the node (typically a unique identifier or business key). Merging on too many properties can lead to unexpected duplicates.

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SET — Updating Properties

The SET clause adds or updates properties on existing nodes and relationships:

Set a single property

MATCH (p:Person {name: "Alice"})
SET p.age = 31
RETURN p

Set multiple properties

MATCH (p:Person {name: "Alice"})
SET p.age = 31, p.email = "alice@example.com"
RETURN p

Set properties from a map

MATCH (p:Person {name: "Alice"})
SET p += {age: 31, city: "London"}
RETURN p

The += operator merges properties — existing properties not in the map are preserved.

Add a label

MATCH (p:Person {name: "Alice"})
SET p:Employee
RETURN p

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REMOVE — Removing Properties and Labels

Remove a property