User-defined variables¶

User-defined variables allow passing the result of one statement to another.

OpenCypher compatibility¶

In openCypher, when you refer to the vertex, edge, or path of a variable, you need to name it first. For example:

nebula> MATCH (v:player{name:"Tim Duncan"}) RETURN v;
+----------------------------------------------------+
| v                                                  |
+----------------------------------------------------+
| ("player100" :player{name: "Tim Duncan", age: 42}) |
+----------------------------------------------------+

The user-defined variable in the preceding query is v.

Native nGQL¶

User-defined variables are written as $var_name. The var_name consists of letters, numbers, or underline characters. Any other characters are not permitted.

The user-defined variables are valid only at the current execution (namely, in this composite query). When the execution ends, the user-defined variables will be automatically expired. The user-defined variables in one statement CANNOT be used in any other clients, executions, or sessions.

You can use user-defined variables in composite queries. Details about composite queries, see Composite queries.

Example¶

nebula> $var = GO FROM "player100" OVER follow YIELD dst(edge) AS id; \
        GO FROM $var.id OVER serve YIELD properties($$).name AS Team, \
        properties($^).name AS Player;
+-----------+-----------------+
| Team      | Player          |
+-----------+-----------------+
| "Spurs"   | "Tony Parker"   |
| "Hornets" | "Tony Parker"   |
| "Spurs"   | "Manu Ginobili" |
+-----------+-----------------+