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Update 1.get-subgraph.md #808

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51 changes: 26 additions & 25 deletions docs-2.0/3.ngql-guide/16.subgraph-and-path/1.get-subgraph.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,8 @@ The `GET SUBGRAPH` statement retrieves information of vertices and edges reachab

```ngql
GET SUBGRAPH [WITH PROP] [<step_count> STEPS] FROM {<vid>, <vid>...}
[IN <edge_type>, <edge_type>...]
[OUT <edge_type>, <edge_type>...]
[BOTH <edge_type>, <edge_type>...];
[{IN | OUT | BOTH} <edge_type>, <edge_type>...]
[YIELD [VERTICES AS <vertex_alias>] [,EDGES AS <edge_alias>]];
```

- `WITH PROP` shows the properties. If not specified, the properties will be hidden.
Expand All @@ -19,6 +18,8 @@ GET SUBGRAPH [WITH PROP] [<step_count> STEPS] FROM {<vid>, <vid>...}

- `edge_type` specifies the edge type. You can use `IN`, `OUT`, and `BOTH` to specify the traversal direction of the edge type. The default is `BOTH`.

- `YIELD` defines the output that needs to be returned. You can return only vertexes or edges. The alias must be set. When you do not use `YIELD` to define the output result, `_vertices` and `_edges` are returned by default.

!!! note

The path type of `GET SUBGRAPH` is `trail`. Only vertices can be repeatedly visited in graph traversal. For more information, see [Path](../../1.introduction/2.1.path.md).
Expand All @@ -32,13 +33,13 @@ The following graph is used as the sample.
* This example goes one step from the vertex `player100` over all edge types and gets the subgraph.

```ngql
nebula> GET SUBGRAPH 1 STEPS FROM "player100";
nebula> GET SUBGRAPH 1 STEPS FROM "player100" YIELD VERTICES AS nodes, EDGES AS relationships;
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
| _vertices | _edges |
| nodes | relationships |
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
| [("player100" :player{})] | [[:serve "player100"->"team200" @0 {}], [:follow "player100"->"player101" @0 {}], [:follow "player100"->"player102" @0 {}]] |
| [("player100" :player{})] | [[:follow "player100"->"player101" @0 {}], [:follow "player100"->"player102" @0 {}], [:serve "player100"->"team200" @0 {}]] |
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
| [("team200" :team{}), ("player101" :player{}), ("player102" :player{})] | [[:follow "player102"->"player101" @0 {}]] |
| [("player101" :player{}), ("player102" :player{}), ("team200" :team{})] | [[:follow "player102"->"player101" @0 {}]] |
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
```

Expand All @@ -49,24 +50,24 @@ The following graph is used as the sample.
* This example goes one step from the vertex `player100` over incoming `follow` edges and gets the subgraph.

```ngql
nebula> GET SUBGRAPH 1 STEPS FROM "player100" IN follow;
+---------------------------+--------+
| _vertices | _edges |
+---------------------------+--------+
| [("player100" :player{})] | [] |
+---------------------------+--------+
| [] | [] |
+---------------------------+--------+
nebula> GET SUBGRAPH 1 STEPS FROM "player100" IN follow YIELD VERTICES AS nodes, EDGES AS relationships;
+---------------------------+---------------+
| nodes | relationships |
+---------------------------+---------------+
| [("player100" :player{})] | [] |
+---------------------------+---------------+
| [] | [] |
+---------------------------+---------------+
```

There is no incoming `follow` edge to `player100`, so no vertex or edge is returned.

* This example goes one step from the vertex `player100` over outgoing `serve` edges, gets the subgraph, and shows the property of the edge.

```ngql
nebula> GET SUBGRAPH WITH PROP 1 STEPS FROM "player100" OUT serve;
nebula> GET SUBGRAPH WITH PROP 1 STEPS FROM "player100" OUT serve YIELD VERTICES AS nodes, EDGES AS relationships;
+------------------------------------------------------+-------------------------------------------------------------------------+
| _vertices | _edges |
| nodes | relationships |
+------------------------------------------------------+-------------------------------------------------------------------------+
| [("player100" :player{age: 42, name: "Tim Duncan"})] | [[:serve "player100"->"team200" @0 {end_year: 2016, start_year: 1997}]] |
+------------------------------------------------------+-------------------------------------------------------------------------+
Expand Down Expand Up @@ -103,12 +104,12 @@ nebula> go 1 steps from "A" over follow;
The query stops when there is not enough subgraph data and will not return the null value.

```ngql
nebula> GET SUBGRAPH 100 STEPS FROM "player141" OUT follow;
+-------------------------------------------------------+--------------------------------------------+
| _vertices | _edges |
+-------------------------------------------------------+--------------------------------------------+
| [("player141" :player{age: 43, name: "Ray Allen"})] | [[:follow "player141"->"player124" @0 {}]] |
+-------------------------------------------------------+--------------------------------------------+
| [("player124" :player{age: 33, name: "Rajon Rondo"})] | [[:follow "player124"->"player141" @0 {}]] |
+-------------------------------------------------------+--------------------------------------------+
nebula> GET SUBGRAPH 100 STEPS FROM "player141" OUT follow YIELD VERTICES AS nodes, EDGES AS relationships;
+---------------------------+--------------------------------------------+
| nodes | relationships |
+---------------------------+--------------------------------------------+
| [("player141" :player{})] | [[:follow "player141"->"player124" @0 {}]] |
+---------------------------+--------------------------------------------+
| [("player124" :player{})] | [[:follow "player124"->"player141" @0 {}]] |
+---------------------------+--------------------------------------------+
```