Count Query Expression

The count query expression derives a single integer—the number of rows returned by a nested query specification.

Syntax
<count query expression> ::= "COUNT {" <query> "}"

Details

• The <query> is executed as a complete query, and COUNT { ... } returns the number of rows it produces. The body must therefore end with a RETURN.
• Because the count is over returned rows, the RETURN should project the matched rows (e.g. RETURN c), not an aggregate. A body like RETURN count(c) produces a single row, so COUNT { ... } would always return 1.

NOTE

Non-standard extension. COUNT { ... } is not part of the GQL standard (ISO/IEC 39075). GQLDB accepts it for convenience, but queries using it run with an advisory warning. Prefer the standard Value Query Expression in new queries.

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

Count the papers each paper cites:

GQL
MATCH (p:Paper)
LET citations = COUNT { MATCH (p)-[:Cites]->(c:Paper) RETURN c }
RETURN p.title, citations

Result:

The standard equivalent, which does not emit a warning:

GQL
MATCH (p:Paper)
LET citations = VALUE { MATCH (p)-[:Cites]->(c:Paper) RETURN count(c) }
RETURN p.title, citations