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apoc.nodes.group

此过程返回只能由其他 APOC 过程访问的虚拟节点。欲了解更多信息，请参阅虚拟节点与关系 (图投影)。

此过程不被认为是多线程安全运行的。因此，并行运行时不支持此过程。欲了解更多信息，请参阅 Cypher 手册 → 并行运行时。

详情
语法	`apoc.nodes.group(labels, groupByProperties [, aggregations, config ]) :: (nodes, relationships, node, relationship)`
描述	允许根据给定属性对 `NODE` 值进行聚合。此过程返回虚拟 `NODE` 值。
输入参数	名称	类型	描述
	`labels`	`LIST<STRING>`	要聚合的节点标签列表。使用 `['*']` 表示应查看所有节点标签。
	`groupByProperties`	`LIST<STRING>`	用于对节点进行分组的属性键。
	`aggregations`	`LIST<MAP>`	第一个映射指定了要聚合的节点属性及其相应的聚合函数，而第二个映射指定了要聚合的关系属性。默认值为：`[{=count}, {=count}]`。
	`config`	`MAP`	`{ includeRels :: STRING \| LIST<STRING> excludeRels :: STRING \| LIST<STRING>, orphans = true :: BOOLEAN, selfRels = true :: BOOLEAN, limitNodes = -1 :: INTEGER, limitRels = -1 :: INTEGER, relsPerNode = -1 :: INTEGER, filter :: MAP }`。默认值为：`{}`。
返回参数	名称	类型	描述
	`nodes`	`LIST<NODE>`	以虚拟节点表示的分组节点列表。
	`relationships`	`LIST<RELATIONSHIP>`	以虚拟关系表示的分组关系列表。
	`node`	`NODE`	分组节点。
	`relationship`	`RELATIONSHIP`	分组关系。

使用示例

本节中的示例基于以下示例图

CREATE
 (alice:Person {name:'Alice', gender:'female', age:32, kids:1}),
 (bob:Person   {name:'Bob',   gender:'male',   age:42, kids:3}),
 (eve:Person   {name:'Eve',   gender:'female', age:28, kids:2}),
 (graphs:Forum {name:'Graphs',    members:23}),
 (dbs:Forum    {name:'Databases', members:42}),
 (alice)-[:KNOWS {since:2017}]->(bob),
 (eve)-[:KNOWS   {since:2018}]->(bob),
 (alice)-[:MEMBER_OF]->(graphs),
 (alice)-[:MEMBER_OF]->(dbs),
 (bob)-[:MEMBER_OF]->(dbs),
 (eve)-[:MEMBER_OF]->(graphs);

CALL apoc.nodes.group(
  ['*'],
  ['gender'],
  [{`*`:'count', age:'min'}, {`*`:'count'} ]
)
YIELD relationships
UNWIND relationships as rel
RETURN apoc.rel.startNode(rel) AS start, rel, apoc.rel.endNode(rel) AS end;

结果
start	rel	end
(:Person {gender: "female", min_age: 28, `count_*`: 2})	[:MEMBER_OF {`count_*`: 3}]	(:Forum {gender: NULL, `count_*`: 2})
(:Person {gender: "female", min_age: 28, `count_*`: 2})	[:KNOWS {`count_*`: 2}]	(:Person {gender: "male", min_age: 42, `count_*`: 1})
(:Person {gender: "female", min_age: 28, `count_*`: 2})	[:KNOWS {`count_*`: 2}]	(:Person {gender: "male", min_age: 42, `count_*`: 1})
(:Person {gender: "male", min_age: 42, `count_*`: 1})	[:MEMBER_OF {`count_*`: 1}]	(:Forum {gender: NULL, `count_*`: 2})

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