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User-defined variables

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

OpenCypher variables

In openCypher, when you refer to a variable of vertex, edge or path, you need to name it first. The name you give to the pattern is a variable. 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.

nGQL extensions

User-defined variables are written as $var_name. The var_name consists of alphanumeric characters. Any other characters are not permitted.

User-defined variables can only be used in one execution. For example, you can use user-defined variables in composite queries separated by semicolon ; or pipe |. Details about composite queries, see Composite queries.

NOTE: A user-defined variable is valid only at the current session and execution.

A user-defined variable in one statement CANNOT be used in either other clients or other executions. The statement that defines the user-defined variable and the statement that uses it must be submitted together. When this session ends, the user-defined variable is automatically expired.

NOTE: User-defined variables are case-sensitive.

Example

nebula> $var = GO FROM "player100" OVER follow YIELD follow._dst AS id; \
GO FROM $var.id OVER serve YIELD $$.team.name AS Team, \
$^.player.name AS Player;
+---------+-------------+
| Team    | Player      |
+---------+-------------+
| Nuggets | Tony Parker |
+---------+-------------+

Last update: March 19, 2021