The NULLIF expression is a conditional expression that compares two values and returns null if they are equal; otherwise, it returns the first value. It is often used to handle cases where specific values should be treated as null, which can be helpful for conditional data cleansing or handling default values.

<nullif expression> ::= 
  "NULLIF" "(" <value expression> "," <value expression> ")"

The NULLIF(V1, V2) expression is equivalent to the following CASE expression:

CASE 
  WHEN V1 = V2 THEN NULL
  ELSE V1
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, NULLIF(n.author, "Alex")

Result: