Fixed length patterns

The most basic form of graph pattern matching in Cypher® involves the matching of fixed length patterns. This includes node patterns, relationship patterns, and path patterns.

Node patterns

Every graph pattern contains at least one node pattern. The simplest graph pattern is a single, empty node pattern:

MATCH ()

The empty node pattern matches every node in a property graph. In order to obtain a reference to the nodes matched, a variable needs to be declared in the node pattern:

MATCH (n)

With this reference, node properties can be accessed:

MATCH (n)
RETURN n.name

Adding a label expression to the node pattern means only nodes with labels that match will be returned. The following matches nodes that have the Stop label:

MATCH (n:Stop)

The following more complex label expression matches all nodes that are either a TrainStation and a BusStation or StationGroup:

MATCH (n:(TrainStation&BusStation)|StationGroup)

A map of property names and values can be used to match on node properties based on equality with the specified values. The following matches nodes that have their mode property equal to Rail:

MATCH (n { mode: 'Rail' })

More general predicates can be expressed with a WHERE clause. The following matches nodes whose name property starts with Preston:

MATCH (n:Station WHERE n.name STARTS WITH 'Preston')

See the node patterns reference section for more details.

Relationship patterns

The simplest possible relationship pattern is a pair of dashes:

--

This pattern matches a relationship with any direction and does not filter on any relationship type or property. Unlike a node pattern, a relationship pattern cannot be used in a MATCH clause without node patterns at both ends. See path patterns for more details.

In order to obtain a reference to the relationships matched by the pattern, a relationship variable needs to be declared in the pattern by adding the variable name in square brackets in between the dashes:

-[r]-

To match a specific direction, add < or > to the left or right hand side respectively:

-[r]->

To match on a relationship type, add the type name after a colon:

-[:CALLS_AT]->

Similar to node patterns, a map of property names and values can be added to filter on properties of the relationship based on equality with the specified values:

-[{ distance: 0.24, duration: 'PT4M' }]->

A WHERE clause can be used for more general predicates:

-[r WHERE time() + duration(r.duration) < time('22:00') ]->

See the relationship patterns reference section for more details.

Path patterns

Any valid path starts and ends with a node, with relationships between each node (if there is more than one node). Fixed length path patterns have the same restrictions, and for all valid path patterns the following are true:

  • They have at least one node pattern.

  • They begin and end with a node pattern.

  • They alternate between nodes and relationships.

These are all valid path patterns:

()
(s)--(e)
(:Station)--()<--(m WHERE m.departs > time('12:00'))-->()-[:NEXT]->(n)

These are invalid path patterns:

-->
()-->
()-->-->()

Path pattern matching

This section contains an example of matching a path pattern to paths in a property graph.

It uses the following graph:

path pattern example graph

To recreate the graph, run the following query against an empty Neo4j database:

CREATE (pmr:Station {name: 'Peckham Rye'}),
  (dmk:Station {name: 'Denmark Hill'}),
  (vic:Station {name: 'London Victoria'}),
  (clp:Station {name: 'Clapham High Street'}),
  (eph:Station {name: 'Elephant & Castle'}),
  (vic)<-[:CALLS_AT]-(s1:Stop {departs: time('11:55')}),
  (dmk)<-[:CALLS_AT]-(s2:Stop {departs: time('11:44')})-[:NEXT]->(s1),
  (pmr)<-[:CALLS_AT]-(s3:Stop {departs: time('11:40')})-[:NEXT]->(s2),
  (clp)<-[:CALLS_AT]-(s4:Stop {departs: time('11:41')}),
  (dmk)<-[:CALLS_AT]-(s5:Stop {departs: time('11:37')})-[:NEXT]->(s4),
  (pmr)<-[:CALLS_AT]-(s6:Stop {departs: time('11:33')})-[:NEXT]->(s5),
  (eph)<-[:CALLS_AT]-(s7:Stop {departs: time('11:54')}),
  (dmk)<-[:CALLS_AT]-(s8:Stop {departs: time('11:47')})-[:NEXT]->(s7),
  (pmr)<-[:CALLS_AT]-(s9:Stop {departs: time('11:44')})-[:NEXT]->(s8)

The graph contains a number of train Stations and Stops. A Stop represents the arrival and departure of a train that CALLS_AT a Station. Each Stop forms part of a sequence of Stops connected by relationships with the type NEXT, representing the order of calling points made by a train service.

The graph shows three chains of Stops that represent different train services. Each of these services calls at the Station with the name Denmark Hill.

To return all Stops that call at the Station Denmark Hill, the following motif is used (the term motif is used to describe the pattern looked for in the graph):

path pattern motif

In this case, three paths in the graph match the structure of the motif (plus the predicate anchoring to the Station Denmark Hill):

path pattern solutions

In order to return the name of each Stop that calls at a Station, declare a variable in the Stop node pattern. The results will then have a row containing the departs value of each Stop for each match shown above:

Query
MATCH (s:Stop)-[:CALLS_AT]->(:Station {name: 'Denmark Hill'})
RETURN s.departs AS departureTime
Table 1. Result
departureTime

"11:44:00Z"

"11:47:00Z"

"11:37:00Z"

Rows: 3