12

在具有几个节点和关系的 Neo4j 数据库中，我试图找出最“流行”的用户（在这种情况下：参与大多数关系的节点）：

START n=node:user('*:*')
MATCH (n)-[r]->(x)
RETURN n
ORDER BY COUNT(r) DESC
LIMIT 10

但是，此查询 (Neo4j 1.9.2) 会导致以下错误：

ThisShouldNotHappenError

开发人员：Andres 声称：不应该这样使用聚合。

StackTrace：org.neo4j.cypher.internal.commands.expressions.AggregationExpression.apply(AggregationExpression.scala:31) org.neo4j.cypher.internal.commands.expressions.AggregationExpression.apply(AggregationExpression.scala:29) org.neo4j。 cypher.internal.pipes.ExtractPipe$$anonfun$internalCreateResults$1$$anonfun$apply$1.apply(ExtractPipe.scala:47) org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$internalCreateResults$1$$anonfun$apply $1.apply(ExtractPipe.scala:45) scala.collection.immutable.Map$Map1.foreach(Map.scala:109) org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$internalCreateResults$1.apply(ExtractPipe. scala:45) org.neo4j.cypher.internal.pipes.ExtractPipe$$anonfun$internalCreateResults$1.apply(ExtractPipe.scala:44) scala.collection.Iterator$$anon$11.next(Iterator.scala:328) org. neo4j.cypher.internal.pipes.TopPipe。internalCreateResults(TopPipe.scala:45) org.neo4j.cypher.internal.pipes.PipeWithSource.createResults(Pipe.scala:69) org.neo4j.cypher.internal.pipes.PipeWithSource.createResults(Pipe.scala:66) org.neo4j.cypher.internal.pipes.PipeWithSource.createResults(Pipe.scala:66) neo4j.cypher.internal.executionplan.ExecutionPlanImpl.org$neo4j$cypher$internal$executionplan$ExecutionPlanImpl$$prepareStateAndResult(ExecutionPlanImpl.scala:164) org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl$$anonfun$getLazyReadonlyQuery$1.apply (ExecutionPlanImpl.scala:139) org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl$$anonfun$getLazyReadonlyQuery$1.apply(ExecutionPlanImpl.scala:138) org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.execute(ExecutionPlanImpl.scala :38) org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:72) org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:76) org.neo4j.cypher.javacompat.ExecutionEngine.execute(ExecutionEngine.java:79) org.neo4j.server.rest.web.CypherService.cypher(CypherService.java:94) java.lang.reflect.Method.invoke(Method.java:第611章）

关于如何以不同方式表达这一点的任何想法？

4

2 回答 2

21

就 neo4j 手册而言，如果您需要在“Order by”中使用聚合，则必须在“Return”中包含聚合，因此您只需在“Return”中添加 count(r)，如下所示,

START n=node:user('*:*')
MATCH (n)-[r]->(x)
RETURN n, COUNT(r)
ORDER BY COUNT(r) DESC
LIMIT 10
于 2013-08-20T12:41:17.633 回答
5

在这里介绍一个WITH：

START n=node:user('*:*')
MATCH (n)-[r]->()
WITH n, count(r) as c
RETURN n, c
ORDER BY c DESC
LIMIT 10
于 2013-08-20T11:41:08.693 回答