neo4j

neo4j简介

• 开源 NoSQL 数据库，原生的图数据库，2003 年开始开发，使用 scala和java 语言，2007年开始发布；
• 世界上最先进的图数据库之一，提供原生的图数据存储，检索和处理；
• 采用属性图模型（Property graph model），极大的完善和丰富图数据模型；
• 专属查询语言 Cypher，直观，高效；

 

图形数据库应用场景：

• 银行欺诈
• 保险欺诈
• 电子商务欺诈
• 工商企业图谱
• 社交网络

Neo4j图数据库中基本元素与概念

• 节点（node）：一个实体记录，就像关系型数据库中的一条记录。一个节点包含多个属性和标签。
• 关系（relationship）：
• 属性（property）：由键值对组成的，就像java当中哈希，
• 标签（lable）：一组拥有相同属性的节点，但不强制要求相同，一个节点可以有多个标签。
• 路径（path）

Cypher查询语言

Cypher是一种生命是图数据库查询语言，类似关系数据库中的SQL。

• MATCH：匹配图模式
• WHERE：过滤条件
• RETURN：定义返回的结果

基本语法：

• 增（CREATE）
• 删（DELETE）
• 改（SET）
• 查（MATCH）
• 函数
• WITCH

 

语法：

<!-- 1. 全表扫描 -->
<!-- mysql -->
SELECT p.*
FROM products as p;

<!-- neo4j -->
MATCH (p:Product)
RETURN p;


<!-- 2. 查询价格最贵的10个商品，只返回商品名字和单价 -->
<!-- mysql -->
SELECT p.ProductName, p.UnitPrice
FROM products as p
ORDER BY p.UnitPrice DESC
LIMIT 10;

<!-- neo4j -->
MATCH (p:Product)
RETURN p.productName, p.unitPrice
ORDER BY p.unitPrice DESC
LIMIT 10;


<!-- 3. 按照商品名字筛选 -->
<!-- mysql -->
SELECT p.ProductName, p.UnitPrice
FROM products AS p
WHERE p.ProductName = 'Chocolade';

<!-- neo4j -->
MATCH (p:Product)
WHERE p.productName = "Chocolade"
RETURN p.productName, p.unitPrice;

<!-- 其他的写法 -->
MATCH (p:Product {productName:"Chocolade"})
RETURN p.productName, p.unitPrice;

<!-- 4. 按照商品名字筛选2 -->
<!-- mysql -->
SELECT p.ProductName, p.UnitPrice
FROM products as p
WHERE p.ProductName IN ('Chocolade','Chai');

<!-- neo4j -->
MATCH (p:Product)
WHERE p.productName IN ['Chocolade','Chai']
RETURN p.productName, p.unitPrice;


<!-- 5. 模糊查询和数值过滤 -->
<!-- mysql -->
SELECT p.ProductName, p.UnitPrice
FROM products AS p
WHERE p.ProductName LIKE 'C%' AND p.UnitPrice > 100;

<!-- neo4j -->
MATCH (p:Product)
WHERE p.productName STARTS WITH "C" AND p.unitPrice > 100
RETURN p.productName, p.unitPrice;


<!-- 6. 多表联合查询-->
<!-- mysql -->
SELECT DISTINCT c.CompanyName
FROM customers AS c
JOIN orders AS o ON (c.CustomerID = o.CustomerID)
JOIN order_details AS od ON (o.OrderID = od.OrderID)
JOIN products AS p ON (od.ProductID = p.ProductID)
WHERE p.ProductName = 'Chocolade';

<!-- neo4j -->
MATCH (p:Product {productName:"Chocolade"})<-[:PRODUCT]-(:Order)<-[:PURCHASED]-(c:Customer)
RETURN distinct c.companyName;


<!-- 7. 分组topN -->
<!-- mysql -->
SELECT e.EmployeeID, count(*) AS Count
FROM Employee AS e
JOIN Order AS o ON (o.EmployeeID = e.EmployeeID)
GROUP BY e.EmployeeID
ORDER BY Count DESC LIMIT 10;

<!-- neo4j -->
MATCH (:Order)<-[:SOLD]-(e:Employee)
RETURN e.name, count(*) AS cnt
ORDER BY cnt DESC LIMIT 10

　　

1优于2

1. MATCH (n) OPTIONAL MATCH (n)-[r]->() RETURN count(n.prop) + count(r.prop);

2. MATCH (n) OPTIONAL MATCH (n)-[r]->() RETURN count(*) + count(*);

 

//增
create (:pig{name:"猪爷爷",age:15});
create (:pig{name:"猪爷爷",age:13});
//查
match (a:pig{name:"猪奶奶"}) match (b:pig{name:"猪爷爷"}) create (a)-[r:夫妻]->(b) return r;
create (:pig{name:"猪爸爸",age:12})-[:夫妻{age:5}]->(:pig{name:"猪妈妈",age:9});
create (:pig{name:"佩奇",age:2})-[:姐弟]->(:pig{name:"乔治",age:1});
match (a:pig{name:"猪爸爸"}) match (b:pig{name:"猪爷爷"}) create (b)-[r:父子]->(a) return r;
match (a:pig{name:"猪爸爸"}) match (b:pig{name:"佩奇"}) create (b)-[r:父女]->(a) return r;
match (a:pig{name:"猪爷爷"}) match (b:pig{name:"佩奇"}) create (b)-[r:孙女]->(a) return r;
match (a:pig{name:"猪奶奶"}) match (b:pig{name:"佩奇"}) create (b)-[r:孙女]->(a) return r;
match (a:pig{name:"猪奶奶"}) match (b:pig{name:"猪爸爸"}) create (b)-[r:母女]->(a) return r;

//改
match (n:pig{name:"猪妈妈"}) set n.age=8

create (:die:pig{name:"猪祖父",age:20}),(:pig{name:"猪祖奶",age:21});
//删
match (n:die) delete n;

match p=allshortestpath((:Star{name:"小明"})-[*..5]->(:Star{name:"王大拿"})) return p;
match (:Star{name:"王大拿"})->() limit 50;

　　csv数据导入

LOAD CSV WITH HEADERS FROM ’file:///data/locations.csv’ AS line
WITH split(line.locations,";") as locations, line.title as title
UNWIND locations AS location  --类似for location in locations
MERGE (x:Location {name:location})
MERGE (m:Movie {title:title})
MERGE (m)-[:FILMED_IN]->(x)

　　

neo4j下载及安装

Download Neo4j 安装在下载成功跳转页下拉内容中有写，需复制“Activation Key”中激活码进行激活

NEO4J安装教程    windows下安装neo4j报错解决  jdk下载地址

Invoke-Neo4j : Cannot validate argument on parameter 'ArgumentList'. The argument is null, empty, or an element of the argument collection contains a null value. Supply a collection that does not contain any null values and then try the command again.

NEO4J_HOME = D:\neo4j-community-4.2.4

path  > ;%NEO4J_HOME%\bin;

 

Neo4j Ecosystem

（1）neo4j browser

 

 （2）neo4j bloom

 

 python 连接 neo4j

# pip3 install neo4j-driver
# python3 example.py

from neo4j import GraphDatabase, basic_auth

driver = GraphDatabase.driver(
  "bolt://<HOST>:<BOLTPORT>",
  auth=basic_auth("<USERNAME>", "<PASSWORD>"))

cypher_query = '''
MATCH (m:Movie {title:$movie})<-[:RATED]-(u:User)-[:RATED]->(rec:Movie) 
RETURN distinct rec.title AS recommendation LIMIT 20
'''

with driver.session(database="neo4j") as session:
  results = session.read_transaction(
    lambda tx: tx.run(cypher_query,
                      movie="Crimson Tide").data())
  for record in results:
    print(record['recommendation'])

driver.close()

　　

 

参考资料：

NoSQL 新贵之崛起的 Neo4j 受益匪浅

知识图谱和 Neo4j 浅析 知识图谱使用场景及neo4j性能方面的介绍

史上最全面的Neo4j使用指南