Property reference¶
You can refer to the properties of a vertex or an edge in WHERE and YIELD syntax.
Note
This function applies to native nGQL only.
Property reference for vertex¶
For source vertex¶
$^.<tag_name>.<prop_name>
| Parameter | Description |
|---|---|
$^ |
is used to get the property of the source vertex. |
tag_name |
is the tag name of the vertex. |
prop_name |
specifies the property name. |
For destination vertex¶
$$.<tag_name>.<prop_name>
| Parameter | Description |
|---|---|
$$ |
is used to get the property of the destination vertex. |
tag_name |
is the tag name of the vertex. |
prop_name |
specifies the property name. |
Property reference for edge¶
For user-defined edge property¶
<edge_type>.<prop_name>
| Parameter | Description |
|---|---|
edge_type |
is the edge type of the edge. |
prop_name |
specifies the property name of the edge type. |
For built-in properties¶
Apart from the user-defined edge property, there are four built-in properties in each edge:
| Parameter | Description |
|---|---|
_src |
source vertex ID of the edge |
_dst |
destination vertex ID of the edge |
_type |
edge type |
_rank |
the rank value for the edge |
Examples¶
The following query returns the name property of the player tag on the source vertex and the age property of the player tag on the destination vertex.
nebula> GO FROM "player100" OVER follow YIELD $^.player.name AS startName, $$.player.age AS endAge;
+--------------+--------+
| startName | endAge |
+--------------+--------+
| "Tim Duncan" | 36 |
| "Tim Duncan" | 41 |
+--------------+--------+
The following query returns the degree property of the edge type follow.
nebula> GO FROM "player100" OVER follow YIELD follow.degree;
+---------------+
| follow.degree |
+---------------+
| 95 |
+---------------+
The following query returns the source vertex, the destination vertex, the edge type, and the edge rank value of the edge type follow.
nebula> GO FROM "player100" OVER follow YIELD follow._src, follow._dst, follow._type, follow._rank;
+-------------+-------------+--------------+--------------+
| follow._src | follow._dst | follow._type | follow._rank |
+-------------+-------------+--------------+--------------+
| "player100" | "player101" | 17 | 0 |
| "player100" | "player125" | 17 | 0 |
+-------------+-------------+--------------+--------------+
Legacy version compatibility
NebulaGraph 2.6.0 and later versions support the new Schema function. Similar statements as the above examples are written as follows in 3.0.0.
GO FROM "player100" OVER follow YIELD properties($^).name AS startName, properties($$).age AS endAge;
GO FROM "player100" OVER follow YIELD properties(edge).degree;
GO FROM "player100" OVER follow YIELD src(edge), dst(edge), type(edge), rank(edge);
In 3.0.0, NebulaGraph is still compatible with the old syntax.