使用Cypher将关系添加到现有节点 [英] Adding relationship to existing nodes with Cypher

问题描述

我是第一次尝试Neo4j.我正在使用2.0-RC1社区版.

I'm trying out Neo4j for the first time. I'm using the 2.0-RC1 community edition.

我已经创建了一些节点:

I've created some nodes:

MERGE (u:User{username:'admin',password:'admin'})
MERGE (r1:Role{name:'ROLE_ADMIN'})
MERGE (r2:Role{name:'ROLE_WEB_USER'})
MERGE (r3:Role{name:'ROLE_REST_USER'})

，现在我想在节点之间添加关系.但是，我不想要清除使用上述脚本创建的现有数据库，添加语句并再次运行它.我想将关系添加到现有节点. Google帮我找到了这个

and now I want to add relationships between the nodes. However, I don't want to clear out the existing database created with the script above, add the statements and run it again. I want to add relationships to the existing nodes. Google helped me find this:

START n=node(*), m=node(*)  
where has(n.username) and has(m.name) and n.username = 'admin' 
and m.name = 'ROLE_WEB_USER' 
create (n)-[:HAS_ROLE]->(m)

哪个工作正常(即使我不了解所有语法).但是，我知道这会找到任何具有username属性的节点和具有name属性的节点，而不是使用标签来检查其节点类型是否正确.

Which works fine (even though I don't understand all the syntax). However, I am aware that this finds any node with a username property and any node with a name property, instead of using labels to check that it has the right type of node.

如何使用标签来做同样的事情?

How can I do the same using labels?

推荐答案

在Neo4j 2.0中，您可以为标签和用于查找的属性创建模式索引:

In Neo4j 2.0 you can create schema indexes for your labels and the properties you use for lookup:

CREATE INDEX ON :User(username)
CREATE INDEX ON :Role(name)

要创建关系，您可以使用:

To create relationships you might use:

MATCH (u:User {username:'admin'}), (r:Role {name:'ROLE_WEB_USER'})
CREATE (u)-[:HAS_ROLE]->(r)

如果可能，MATCH将使用索引.如果没有索引，它将查找所有带有标签的节点，并查看属性是否匹配.

The MATCH will use an index if possible. If there is no index, it will lookup up all nodes carrying the label and see if the property matches.

以上语法仅适用于Neo4j 2.0.0-RC1及更高版本.

N.B. the syntax above will only work with Neo4j 2.0.0-RC1 and above.

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