QueryingClausesOPTIONAL MATCH

OPTIONAL MATCH clause

The MATCH clause can be modified by prepending the OPTIONAL keyword. OPTIONAL MATCH clause behaves the same as a regular MATCH, but when it fails to find the pattern, missing parts of the pattern will be filled with null values.

  1. Get optional relationships
  2. Optional typed and named relationship

Dataset

The following examples are executed with this dataset. You can create this dataset locally by executing the queries at the end of the page: Dataset queries.

Data set

1. Get optional relationships

Using OPTIONAL MATCH when returning a relationship that doesn’t exist will return the default value NULL instead.

The returned property of an optional element that is NULL will also be NULL:

MATCH (c1:Country {name: 'France'})
OPTIONAL MATCH (c1)--(c2:Country {name: 'Germany'})
RETURN c2;

Output:

+------+
| c2   |
+------+
| Null |
+------+

2. Optional typed and named relationship

The OPTIONAL MATCH clause allows you to use the same conventions as MATCH when it comes to handling variables and relationship types:

MATCH (c:Country {name: 'United Kingdom'})
OPTIONAL MATCH (c)-[r:LIVES_IN]->()
RETURN c.name, r;

Output:

+----------------+----------------+
| c.name         | r              |
+----------------+----------------+
| United Kingdom | Null           |
+----------------+----------------+

Because there are no outgoing relationships of type LIVES_IN for the node, the value of r is null while the value of country.name is 'United Kingdom'.

Dataset queries

We encourage you to try out the examples by yourself. You can get our dataset locally by executing the following query block.

MATCH (n) DETACH DELETE n;
 
CREATE (c1:Country {name: 'Germany', language: 'German', continent: 'Europe', population: 83000000});
CREATE (c2:Country {name: 'France', language: 'French', continent: 'Europe', population: 67000000});
CREATE (c3:Country {name: 'United Kingdom', language: 'English', continent: 'Europe', population: 66000000});
 
MATCH (c1),(c2)
WHERE c1.name= 'Germany' AND c2.name = 'France'
CREATE (c2)<-[:WORKING_IN {date_of_start: 2014}]-(p:Person {name: 'John'})-[:LIVING_IN {date_of_start: 2014}]->(c1);
 
MATCH (c)
WHERE c.name= 'United Kingdom'
CREATE (c)<-[:WORKING_IN {date_of_start: 2014}]-(p:Person {name: 'Harry'})-[:LIVING_IN {date_of_start: 2013}]->(c);
 
MATCH (p1),(p2)
WHERE p1.name = 'John' AND p2.name = 'Harry'
CREATE (p1)-[:FRIENDS_WITH {date_of_start: 2011}]->(p2);
 
MATCH (p1),(p2)
WHERE p1.name = 'John' AND p2.name = 'Harry'
CREATE (p1)<-[:FRIENDS_WITH {date_of_start: 2012}]-(:Person {name: 'Anna'})-[:FRIENDS_WITH {date_of_start: 2014}]->(p2);
 
MATCH (p),(c1),(c2)
WHERE p.name = 'Anna' AND c1.name = 'United Kingdom' AND c2.name = 'Germany'
CREATE (c2)<-[:LIVING_IN {date_of_start: 2014}]-(p)-[:LIVING_IN {date_of_start: 2014}]->(c1);
 
MATCH (n)-[r]->(m) RETURN n,r,m;
MERGEPROFILE