The Neo4j Graph Database
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3.2.Relationships
Relationships between nodes are a key part of a graph database. They allow for finding related data.
Just like nodes, relationships can have properties.
A Relationship
Start node
has a
End node
has a
Relationship type
has a
Properties
can have
Name
uniquely identified by
A relationship connects two nodes, and is guaranteed to have valid start and end nodes.
Start node End node
relationship
As relationships are always directed, they can be viewed as outgoing or incoming relative to a node,
which is useful when traversing the graph:
Node
incoming relationship outgoing relationship
Relationships are equally well traversed in either direction. This means that there is no need to add
duplicate relationships in the opposite direction (with regard to traversal or performance).
While relationships always have a direction, you can ignore the direction where it is not useful in your
application.
Note that a node can have relationships to itself as well:
To further enhance graph traversal all relationships have a relationship type. Note that the word type
might be misleading here, you could rather think of it as a label. The following example shows a
simple social network with two relationship types.
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