db

neo4j 学习笔记

一些基本概念，从官网copy过来的，如下：

Graph Fundamentals

Basic concepts to get you going.

A graph database can store any kind of data using a few simple concepts:

  1. Nodes - graph data records
  2. Relationships - connect nodes
  3. Properties - named data values

A Graph Database

Neo4j stores data in a Graph, with records called Nodes.

The simplest graph has just a single node with some named values called Properties. Let’s draw a social graph of our friends on the Neo4j team:

  1. Start by drawing a circle for the node
  2. Add the name Emil
  3. Note that he is from Sweden
  • Nodes are the name for data records in a graph
  • Data is stored as Properties
  • Properties are simple name/value pairs

Labels

Associate a set of nodes.

Nodes can be grouped together by applying a Label to each member. In our social graph, we’ll label each node that represents a Person.

  1. Apply the label “Person” to the node we created for Emil
  2. Color “Person” nodes red
  • A node can have zero or more labels
  • Labels do not have any properties

More Nodes

Schema-free, nodes can have a mix of common and unique properties.

Like any database, storing data in Neo4j can be as simple as adding more records. We’ll add a few more nodes:

  1. Emil has a klout score of 99
  2. Johan, from Sweden, who is learning to surf
  3. Ian, from England, who is an author
  4. Rik, from Belgium, has a cat named Orval
  5. Allison, from California, who surfs
  • Similar nodes can have different properties
  • Properties can be strings, numbers, or booleans
  • Neo4j can store billions of nodes

Consider Relationships

Connect nodes in the graph

The real power of Neo4j is in connected data. To associate any two nodes, add a Relationship which describes how the records are related.

In our social graph, we simply say who KNOWS whom:

  1. Emil KNOWS Johan and Ian
  2. Johan KNOWS Ian and Rik
  3. Rik and Ian KNOWS Allison
  • Relationships always have direction
  • Relationships always have a type
  • Relationships form patterns of data

Relationship properties

Store information shared by two nodes.

In a property graph, relationships are data records that can also contain properties. Looking more closely at Emil’s relationships, note that:

  • Emil has known Johan since 2001
  • Emil rates Ian 5 (out of 5)
  • Everyone else can have similar relationship properties

可以使用这种方式访问neo4j数据库：

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http://localhost:7474/browser/

清空neo4j数据库

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match(n)
optional match(n)-[r]-()
delete n,r

执行上面的命令后，会删除节点及与该节点相关的关系，但是property keys删不干净

未完，待续……