Value Query Expression

The value query expression allows you to specify a scalar value derived from a nested query specification. The output of this expression is expected to be either a single value or null.

Syntax
<value query expression> ::= "VALUE {" <query> "}"

Details

• The <query> is executed as a complete query and must end with a RETURN that projects exactly one return item (a single column). Returning more than one column raises an error.
• The query must evaluate to at most one row:
  • No rows: the expression yields null.
  • Exactly one row: that single value is returned.
  • More than one row: the query raises an error.
• To guarantee a single row, have the return item use an aggregation function (e.g. avg(), count()) or add an explicit LIMIT 1 to the body.

Example Graph

GQL
INSERT (p1:Paper {_id:'P1', title:'Efficient Graph Search', score:6}),
       (p2:Paper {_id:'P2', title:'Optimizing Queries', score:9}),
       (p3:Paper {_id:'P3', title:'Path Patterns', score:7}),
       (p1)-[:Cites]->(p2),
       (p2)-[:Cites]->(p3)

Examples

GQL
LET avgScore = VALUE {MATCH (n) RETURN avg(n.score)}
MATCH (n) WHERE n.score > avgScore
RETURN n.title

Result: