UNWIND¶

UNWIND transform a list into a sequence of rows.

UNWIND can be used as an individual statement or as a clause within a statement.

UNWIND statement¶

Syntax¶

UNWIND <list> AS <alias> <RETURN clause>;

Examples¶

To transform a list.

nebula> UNWIND [1,2,3] AS n RETURN n;
+---+
| n |
+---+
| 1 |
| 2 |
| 3 |
+---+

UNWIND clause¶

Syntax¶

The UNWIND clause in native nGQL statements.

Note

To use a UNWIND clause in a native nGQL statement, use it after the | operator and use the $- prefix for variables. If you use a statement or clause after the UNWIND clause, use the | operator and use the $- prefix for variables.
```
<statement> | UNWIND $-.<var> AS <alias> <|> <clause>;
```

The UNWIND clause in openCypher statements.

<statement> UNWIND <list> AS <alias> <RETURN clause>；

Examples¶

To transform a list of duplicates into a unique set of rows using WITH DISTINCT in a UNWIND clause.

Note

WITH DISTINCT is not available in native nGQL statements.

// Transform the list `[1,1,2,2,3,3]` into a unique set of rows, sort the rows, and then transform the rows into a list of unique values.

nebula> WITH [1,1,2,2,3,3] AS n \
        UNWIND n AS r \
        WITH DISTINCT r AS r \
        ORDER BY r \
        RETURN collect(r);
+------------+
| collect(r) |
+------------+
| [1, 2, 3]  |
+------------+

To use an UNWIND clause in a MATCH statement.

// Get a list of the vertices in the matched path, transform the list into a unique set of rows, and then transform the rows into a list. 

nebula> MATCH p=(v:player{name:"Tim Duncan"})--(v2) \
        WITH nodes(p) AS n \
        UNWIND n AS r \
        WITH DISTINCT r AS r \
        RETURN collect(r);
+----------------------------------------------------------------------------------------------------------------------+
| collect(r)                                                                                                           |
+----------------------------------------------------------------------------------------------------------------------+
| [("player100" :player{age: 42, name: "Tim Duncan"}), ("player101" :player{age: 36, name: "Tony Parker"}),            |
|("team204" :team{name: "Spurs"}), ("player102" :player{age: 33, name: "LaMarcus Aldridge"}),                          |
|("player125" :player{age: 41, name: "Manu Ginobili"}), ("player104" :player{age: 32, name: "Marco Belinelli"}),       |
|("player144" :player{age: 47, name: "Shaquile O'Neal"}), ("player105" :player{age: 31, name: "Danny Green"}),         |
|("player113" :player{age: 29, name: "Dejounte Murray"}), ("player107" :player{age: 32, name: "Aron Baynes"}),         |
|("player109" :player{age: 34, name: "Tiago Splitter"}), ("player108" :player{age: 36, name: "Boris Diaw"})]           |  
+----------------------------------------------------------------------------------------------------------------------+

To use an UNWIND clause in a GO statement.

// Query the vertices in a list for the corresponding edges with a specified statement.

nebula> YIELD ['player101', 'player100'] AS a | UNWIND $-.a AS  b | GO FROM $-.b OVER follow YIELD edge AS e;
+----------------------------------------------------+
| e                                                  |
+----------------------------------------------------+
| [:follow "player101"->"player100" @0 {degree: 95}] |
| [:follow "player101"->"player102" @0 {degree: 90}] |
| [:follow "player101"->"player125" @0 {degree: 95}] |
| [:follow "player100"->"player101" @0 {degree: 95}] |
| [:follow "player100"->"player125" @0 {degree: 95}] |
+----------------------------------------------------+

To use an UNWIND clause in a LOOKUP statement.

// Find all the properties of players whose age is greater than 46, get a list of unique properties, and then transform the list into rows. 

nebula> LOOKUP ON player \
        WHERE player.age > 46 \
        YIELD DISTINCT keys(vertex) as p | UNWIND $-.p as a | YIELD $-.a AS a;
+--------+
| a      |
+--------+
| "age"  |
| "name" |
+--------+

To use an UNWIND clause in a FETCH statement.

// Query player101 for all tags related to player101, get a list of the tags and then transform the list into rows.

nebula> CREATE TAG hero(like string, height int);
        INSERT VERTEX hero(like, height) VALUES "player101":("deep", 182);
        FETCH PROP ON * "player101" \
        YIELD tags(vertex) as t | UNWIND $-.t as a | YIELD $-.a AS a;
+----------+
| a        |
+----------+
| "hero"   |
| "player" |
+----------+

To use an UNWIND clause in a GET SUBGRAPH statement.

// Get the subgraph including outgoing and incoming serve edges within 0~2 hops from/to player100, and transform the result into rows.

nebula> GET SUBGRAPH 2 STEPS FROM "player100" BOTH serve \
        YIELD edges as e | UNWIND $-.e as a | YIELD $-.a AS a;
+----------------------------------------------+
| a                                            |
+----------------------------------------------+
| [:serve "player100"->"team204" @0 {}]        |
| [:serve "player101"->"team204" @0 {}]        |
| [:serve "player102"->"team204" @0 {}]        |
| [:serve "player103"->"team204" @0 {}]        |
| [:serve "player105"->"team204" @0 {}]        |
| [:serve "player106"->"team204" @0 {}]        |
| [:serve "player107"->"team204" @0 {}]        |
| [:serve "player108"->"team204" @0 {}]        |
| [:serve "player109"->"team204" @0 {}]        |
| [:serve "player110"->"team204" @0 {}]        |
| [:serve "player111"->"team204" @0 {}]        |
| [:serve "player112"->"team204" @0 {}]        |
| [:serve "player113"->"team204" @0 {}]        |
| [:serve "player114"->"team204" @0 {}]        |
| [:serve "player125"->"team204" @0 {}]        |
| [:serve "player138"->"team204" @0 {}]        |
| [:serve "player104"->"team204" @20132015 {}] |
| [:serve "player104"->"team204" @20182019 {}] |
+----------------------------------------------+

To use an UNWIND clause in a FIND PATH statement.

// Find all the vertices in the shortest path from player101 to team204 along the serve edge, and transform the result into rows. 

nebula> FIND SHORTEST PATH FROM "player101" TO "team204" OVER serve \
        YIELD path as p | YIELD nodes($-.p) AS nodes | UNWIND $-.nodes AS a | YIELD $-.a AS a;
+---------------+
| a             |
+---------------+
| ("player101") |
| ("team204")   |
+---------------+

Last update: September 7, 2022