The MATCHNUM function returns a number that uniquely identifies a match in a set of matches.

The numbers are not necessarily consecutive, and gaps may appear (for instance, when matches are filtered out). Rows returned from GRAPH_TABLE have unique match numbers unless ONE ROW PER VERTEX or ONE ROW PER STEP is specified, in which case the same match number is returned for different iterations within a match.

MATCHNUM can be used only in the COLUMNS clause of the SQL graph query as shown.

SELECT *
FROM GRAPH_TABLE ( g
       MATCH (p IS person)
       COLUMNS (MATCHNUM() AS matchnum,
                p.name)
)ORDER BY matchnum;

The preceding graph query matches all person vertices and for each match returns a unique match number as well as the name of the person.

See Example 5-19 for more information.