GO
GO
用指定的过滤条件遍历图,并返回结果。
openCypher兼容性
本文操作仅适用于nGQL扩展。
语法
GO [[<M> TO] <N> STEPS ] FROM <vertex_list>
OVER <edge_type_list> [{REVERSELY | BIDIRECT}]
[ WHERE <conditions> ]
[YIELD [DISTINCT] <return_list>]
[| ORDER BY <expression> [{ASC | DESC}]]
[| LIMIT [<offset_value>,] <number_rows>]
GO [[<M> TO] <N> STEPS ] FROM <vertex_list>
OVER <edge_type_list> [{REVERSELY | BIDIRECT}]
[ WHERE <conditions> ]
[| GROUP BY {col_name | expr | position} YIELD <col_name>]
<vertex_list> ::=
<vid> [, <vid> ...]
<edge_type_list> ::=
edge_type [, edge_type ...]
| *
<return_list> ::=
<col_name> [AS <col_alias>] [, <col_name> [AS <col_alias>] ...]
<N> STEPS
:指定跳数。如果没有指定跳数,默认值N
为1
。如果N
为0
,Nebula Graph不会检索任何边。M TO N STEPS
:遍历M~N
跳的边。如果M
为0
,输出结果和M
为1
相同,即GO 0 TO 2
和GO 1 TO 2
是相同的。<vertex_list>
:用逗号分隔的点ID列表,或特殊的引用符$-.id
。详情请参见管道符。<edge_type_list>
:遍历的边类型列表。REVERSELY | BIDIRECT
:默认情况下检索的是<vertex_list>
的出边,REVERSELY
表示反向,即检索入边,BIDIRECT
表示双向,即检索出边和入边。WHERE <conditions>
:指定遍历的过滤条件。您可以在起始点、目的点和边使用WHERE
子句,还可以结合AND
、OR
、NOT
、XOR
一起使用。详情请参见WHERE。说明:遍历多个边类型时,
WHERE
子句有一些限制。例如不支持WHERE edge1.prop1 > edge2.prop2
。YIELD [DISTINCT] <return_list>
:指定输出结果。详情请参见YIELD。如果没有指定,默认返回目的点ID。ORDER BY
:指定输出结果的排序规则。详情请参见ORDER BY。说明:没有指定排序规则时,输出结果的顺序不是固定的。
LIMIT
:限制输出结果的行数。详情请参见LIMIT。GROUP BY
:根据指定属性的值将输出分组。详情请参见GROUP BY。
示例
# 返回player102所属队伍。
nebula> GO FROM "player102" OVER serve;
+------------+
| serve._dst |
+------------+
| "team203" |
+------------+
| "team204" |
+------------+
# 返回距离player102两跳的朋友。
nebula> GO 2 STEPS FROM "player102" OVER follow;
+-------------+
| follow._dst |
+-------------+
| "player101" |
+-------------+
| "player125" |
+-------------+
...
# 添加过滤条件。
nebula> GO FROM "player100", "player102" OVER serve \
WHERE serve.start_year > 1995 \
YIELD DISTINCT $$.team.name AS team_name, serve.start_year AS start_year, $^.player.name AS player_name;
+-----------------+------------+---------------------+
| team_name | start_year | player_name |
+-----------------+------------+---------------------+
| "Spurs" | 1997 | "Tim Duncan" |
+-----------------+------------+---------------------+
| "Trail Blazers" | 2006 | "LaMarcus Aldridge" |
+-----------------+------------+---------------------+
| "Spurs" | 2015 | "LaMarcus Aldridge" |
+-----------------+------------+---------------------+
# 遍历多个边类型。属性没有值时,会显示__EMPTY__。
nebula> GO FROM "player100" OVER follow, serve \
YIELD follow.degree, serve.start_year;
+---------------+------------------+
| follow.degree | serve.start_year |
+---------------+------------------+
| 95 | __EMPTY__ |
+---------------+------------------+
| 95 | __EMPTY__ |
+---------------+------------------+
| __EMPTY__ | 1997 |
+---------------+------------------+
# 返回player100的入边。
nebula> GO FROM "player100" OVER follow REVERSELY \
YIELD follow._dst AS destination;
+-------------+
| destination |
+-------------+
| "player101" |
+-------------+
| "player102" |
+-------------+
...
# 该MATCH查询与上一个GO查询具有相同的语义。
nebula> MATCH (v)<-[e:follow]- (v2) WHERE id(v) == 'player100' \
RETURN id(v2) AS destination;
+-------------+
| destination |
+-------------+
| "player101" |
+-------------+
| "player102" |
+-------------+
...
# 查询player100的朋友和朋友所属队伍。
nebula> GO FROM "player100" OVER follow REVERSELY \
YIELD follow._dst AS id | \
GO FROM $-.id OVER serve \
WHERE $^.player.age > 20 \
YIELD $^.player.name AS FriendOf, $$.team.name AS Team;
+---------------------+-----------------+
| FriendOf | Team |
+---------------------+-----------------+
| "Tony Parker" | "Spurs" |
+---------------------+-----------------+
| "Tony Parker" | "Hornets" |
+---------------------+-----------------+
...
# 该MATCH查询与上一个GO查询具有相同的语义。
nebula> MATCH (v)<-[e:follow]- (v2)-[e2:serve]->(v3) \
WHERE id(v) == 'player100' \
RETURN v2.name AS FriendOf, v3.name AS Team;
+---------------------+-----------------+
| FriendOf | Team |
+---------------------+-----------------+
| "Tony Parker" | "Spurs" |
+---------------------+-----------------+
| "Tony Parker" | "Hornets" |
+---------------------+-----------------+
...
# 返回player102的出边和入边。
nebula> GO FROM "player102" OVER follow BIDIRECT \
YIELD follow._dst AS both;
+-------------+
| both |
+-------------+
| "player100" |
+-------------+
| "player101" |
+-------------+
...
# 该MATCH查询与上一个GO查询具有相同的语义。
nebula> MATCH (v) -[e:follow]-(v2) \
WHERE id(v)== "player102" \
RETURN id(v2) AS both;
+-------------+
| both |
+-------------+
| "player101" |
+-------------+
| "player103" |
+-------------+
...
# 查询player100 1~2跳内的朋友。
nebula> GO 1 TO 2 STEPS FROM "player100" OVER follow \
YIELD follow._dst AS destination;
+-------------+
| destination |
+-------------+
| "player101" |
+-------------+
| "player125" |
+-------------+
...
# 该MATCH查询与上一个GO查询具有相同的语义。
nebula> MATCH (v) -[e:follow*1..2]->(v2) \
WHERE id(v) == "player100" \
RETURN id(v2) AS destination;
+-------------+
| destination |
+-------------+
| "player100" |
+-------------+
| "player102" |
+-------------+
# 根据年龄分组。
nebula> GO 2 STEPS FROM "player100" OVER follow \
YIELD follow._src AS src, follow._dst AS dst, $$.player.age AS age \
| GROUP BY $-.dst \
YIELD $-.dst AS dst, collect_set($-.src) AS src, collect($-.age) AS age
+-------------+----------------------------+----------+
| dst | src | age |
+-------------+----------------------------+----------+
| "player125" | ["player101"] | [41] |
+-------------+----------------------------+----------+
| "player100" | ["player125", "player101"] | [42, 42] |
+-------------+----------------------------+----------+
| "player102" | ["player101"] | [33] |
+-------------+----------------------------+----------+
# 分组并限制输出结果的行数。
nebula> $a = GO FROM "player100" OVER follow YIELD follow._src AS src, follow._dst AS dst; \
GO 2 STEPS FROM $a.dst OVER follow \
YIELD $a.src AS src, $a.dst, follow._src, follow._dst \
| ORDER BY $-.src | OFFSET 1 LIMIT 2;
+-------------+-------------+-------------+-------------+
| src | $a.dst | follow._src | follow._dst |
+-------------+-------------+-------------+-------------+
| "player100" | "player125" | "player100" | "player101" |
+-------------+-------------+-------------+-------------+
| "player100" | "player101" | "player100" | "player125" |
+-------------+-------------+-------------+-------------+