The COALESCE
expression is a conditional expression that returns the first non-null value from a list of provided expressions. This is useful for substituting a default value when encountering null values, especially in scenarios where you want to avoid null results in calculations or display.
<coalesce expression> ::=
"COALESCE" "(" <value expression> { "," <value expression> }... ")"
The COALESCE(V1, V2, V3)
expression is equivalent to the following CASE
expression:
CASE
WHEN NOT V1 IS NULL THEN V1
WHEN NOT V2 IS NULL THEN V2
ELSE V3
END
Example Graph
The following examples run against this graph:

To create this graph, run the following query against an empty graph:
INSERT (p1:Paper {_id:'P1', title:'Efficient Graph Search', score:6, author:'Alex', publisher:'PulsePress'}),
(p2:Paper {_id:'P2', title:'Optimizing Queries', score:9, author:'Alex'}),
(p3:Paper {_id:'P3', title:'Path Patterns', score:7, author:'Zack', publisher:'BrightLeaf'}),
(p1)-[:Cites {weight:2}]->(p2),
(p2)-[:Cites {weight:1}]->(p3)
Example
MATCH (n:Paper)
RETURN n.title, COALESCE(n.publisher, "N/A") AS publisher
Result:
n.title | publisher |
---|---|
Efficient Graph Search | PulsePress |
Optimizing Queries | N/A |
Path Patterns | BrightLeaf |