一、Neo4j环境搭建

Neo4jHigh-performance graph database from introductory to practical learning video
neo4j官方下载连接

window傻瓜式安装,点击下一步下一步

Introduction to the homepage interface

二、Neo4j构建的元素

节点

A node represents a concrete entity.
节点可以包含：
一个或多个属性
一个或多个标签

关系

Relationships are used to connect2个节点
Relationships can contain：
一个或多个属性
一个或多个标签
要注意的是：
Relationships are directional,而且有3种情况：one way left、One way to the right、双向.但是neo4jIt seems that the bidirectional relationship is not implemented.To implement a bidirectional relationship in business,It seems to pass2a one-way relationship

标签

类似于java的类的概念,Define a certain type of node or a certain type of relationship.
比如：The label of Zhang's three nodes is person,The label of Li's fourth node is also a person;For example, the label of brotherhood is family,The label of sibling relationship is also family.
Tags can be indexed,So building appropriate tags can improve search speed

语法：

:标签1
:标签1:标签2
比如：CREATE (n:西游记:人物 {name:'张三'}) RETURN n

属性

Both nodes and relationships can have one or more properties.
语法：

{属性key："属性value", 属性key："属性value"}

三、CQL

CQL代表Cypher查询语言,The query language used to query the gallery,类比SQLUsed to query relational databases.

理解CQL

节点（Parentheses indicate nodes）

CQL中,（）表示一个节点.比如：(n:person {name:‘如来’})
（）表示一个节点
nIndicates an alias for this node
personIndicates that a label is set for this node
{}Indicates what properties to set for this node

关系（Brackets indicate relationships）

CQL中,[]表示一个关系.There must be nodes on both sides of the relationship,And to set the direction,比如

 () - [] -> ()

但在neo4j中,A relationship can only have one direction,Cannot point to two nodes at the same time.
But it is allowed that the start node and end node of a relationship are themselves.

CREATE

创建一个节点

# 下面两个是等价的
CREATE ()
CREATE (n) 

# 只不过CREATE(n) It is equivalent to giving this node an alias,可以直接RETURN
CREATE (n) RETURN n

# 创建一个节点
CREATE (n:西游记{name: "孙悟空"})
# 一次性创建多个节点
CREATE (n:西游记 {name: "猪八戒"}), (m:西游记 {name: "沙僧"})

创建关系

# 创建新的节点,And at the same time create a relationship for the new node
CREATE (n:`西游记`{name:"唐僧"}) - [r:`坐骑`{attr:"属性"}]-> (m:`西游记`{name:"白龙马"})
return n, m

# between nodes that have already been created,创建1条关系
MATCH (n:`西游记`{name:"孙悟空"}), (m:`西游记`{name:"猪八戒"})
CREATE (n) -[r:师弟{attr:"属性"}]-> (m)
return n, m

# between nodes that have already been created,Create multiple relationships
MATCH (swk:`西游记`{name:"孙悟空"}), (zbj:`西游记`{name:"猪八戒"}), (ss:`西游记`{name:"沙僧"}), (ts:`西游记`{name:"唐僧"})
CREATE (swk) -[:师傅{attr:"属性"}]-> (ts), (zbj) -[:师傅{attr:"属性"}]-> (ts), (ss) -[:师傅{attr:"属性"}]-> (ts)
return swk, zbj, ss

# neo4j,Relationships can point to themselves
MATCH (n:`学习` {name:'张三'})
CREATE (n)-[:自恋]->(n)
RETURN n

DELETE

删除所有节点和关系

MATCH (n)
OPTIONAL MATCH (n)-[r]-()
DELETE n,r

或

MATCH (n) DETACH DELETE n

根据idto delete a single node

MATCH (n) 
WHERE id(n)=4
DELETE n
RETURN n

根据idto delete a single relationship

MATCH  ()-[r]-() Where ID(r)=4 Delete r 

根据2node and relationship direction,删除关系

# Build test data
CREATE (:`学习` {name: '张三'}),(:`学习` {name: '李四'}),(:`学习` {name: '王五'});
MATCH (p1:`学习` {name: '张三'}), (p2:`学习` {name: '李四'}), (p3:`学习` {name: '王五'})
CREATE (p1)-[:认识]->(p2)-[:认识]->(p1)-[:认识]->(p3)
RETURN p1,p2,p3

# Delete the relationship between Zhang San and Li Si,Keep Li Si to know Zhang San
MATCH (n:`学习` {name:'张三'}),(m:`学习` {name:'李四'})
OPTIONAL MATCH (n)-[r]->(m)
DELETE r

Also deletes the specified node and its relationship

# Build test data
CREATE (:`学习` {name: '张三'}),(:`学习` {name: '李四'}),(:`学习` {name: '王五'});
MATCH (p1:`学习` {name: '张三'}), (p2:`学习` {name: '李四'}), (p3:`学习` {name: '王五'})
CREATE (p1)-[:认识]->(p2)-[:认识]->(p1)-[:认识]->(p3)
RETURN p1,p2,p3

# Delete Zhang three nodes,At the same time, delete the relationship with Zhang San
MATCH (n:`学习` {name:'张三'})
OPTIONAL MATCH (n)-[r]-()
DELETE n,r

或

MATCH (n学习` {name:'张三'}) DETACH DELETE n

MATCH

match关键字相当于sql的select

# 相当于select *
MATCH (n)
RETURN n

导入导出

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