Writing New Data

For adding new data, you can use the following clauses.

You can still use the RETURN clause to produce results after writing, but it is not mandatory.

Details on which kind of data can be stored in Memgraph can be found in Data Storage chapter.

CREATE

This clause is used to add new nodes and edges to the database. The creation is done by providing a pattern, similarly to MATCH clause.

For example, to create 2 new nodes connected with a new edge, use this query.

CREATE (node1)-[:edge_type]->(node2)

Labels and properties can be set during creation using the same syntax as in MATCH patterns. For example, creating a node with a label and a property:

CREATE (node :Label {property: "my property value"})

Additional information on CREATE is here.

SET

The SET clause is used to update labels and properties of already existing data.

Example. Incrementing everyone's age by 1.

MATCH (n :Person) SET n.age = n.age + 1

Click here for a more detailed explanation on what can be done with SET.

DELETE

This clause is used to delete nodes and edges from the database.

Example. Removing all edges of a single type.

MATCH ()-[edge :type]-() DELETE edge

When testing the database, you want to often have a clean start by deleting every node and edge in the database. It is reasonable that deleting each node should delete all edges coming into or out of that node.

MATCH (node) DELETE node

But, openCypher prevents accidental deletion of edges. Therefore, the above query will report an error. Instead, you need to use the DETACH keyword, which will remove edges from a node you are deleting. The following should work and delete everything in the database.

MATCH (node) DETACH DELETE node

More examples are here.

REMOVE

The REMOVE clause is used to remove labels and properties from nodes and edges.

Example.

MATCH (n :WrongLabel) REMOVE n :WrongLabel, n.property

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