2024-10-24-neo4j-3-cypher

(matrix:Movie)

(matrix:Movie {title: “The Matrix”})

(matrix:Movie {title: “The Matrix”, released: 1997})

Movie是Node的标签，表明节点的类型。不同的标签可以组成不同的模式，比如Movie和Actor就可以组成一种模式。Neo4j的节点使用标签索引的，每一个索引由标签和属性组成。 节点的属性由大括号包含一系列key/value。比如 {title: "The Matrix", released: 1997}

Relation语法

Cypher中--表示无方向性的关系，<--,-->表示指向性的关系，[....]表示对关系的说明，可以是变量、属性等。

–>

-[role]->

-[:ACTED_IN]->

-[role:ACTED_IN]->

-[role:ACTED_IN {roles: [“Neo”]}]->

ACTED_IN是关系的标签，指明关系的类型。role是关系变量，可以在别处使用。roles是属性值，和节点的属性一样。

Pattern语法

(keanu:Person:Actor {name: “Keanu Reeves”} )-[role:ACTED_IN {roles: [“Neo”] } ]->(matrix:Movie {title: “The Matrix”} )

Pattern指明在图中符合给定pattern的节点以及连接的关系。 Pattern还可以被声明为一个变量：

acted_in = (:Person)-[:ACTED_IN]->(:Movie)

Cypher示例

打开命令行执行：

sudo bin/neo4j console

打开浏览器打开：

http://localhost:7474/browser/

添加：

CREATE (:Movie { title:“The Matrix”,released:1997 })

执行完毕可以看到：


如果创建之后需要返回值：

CREATE (p:Person { name:“Keanu Reeves”, born:1964 })

RETURN p

执行完毕可以看到：


更为复杂的一个例子：

CREATE (a:Person { name:“Tom Hanks”,

born:1956 })-[r:ACTED_IN { roles: [“Forrest”]}]->(m:Movie { title:“Forrest Gump”,released:1994 })

CREATE (d:Person { name:“Robert Zemeckis”, born:1951 })-[:DIRECTED]->(m)

RETURN a,d,r,m


查找

比方说查找所有的Movie：

MATCH (m:Movie)

RETURN m


也可以找某个具体的人：

MATCH (p:Person { name:“Keanu Reeves” })

RETURN p


还可以查找某个关系：

MATCH (p:Person { name:“Tom Hanks” })-[r:ACTED_IN]->(m:Movie)

RETURN m, r


创建新的pattern

MATCH (p:Person { name:“Tom Hanks” })

CREATE (m:Movie { title:“Cloud Atlas”,released:2012 })

CREATE §-[r:ACTED_IN { roles: [‘Zachry’]}]->(m)

RETURN p,r,m


MERGE

Merge表示为节点或者关系添加新的pattern或属性。

添加新的属性：

MERGE (m:Movie { title:“Cloud Atlas” })

ON CREATE SET m.released = 2012

RETURN m


添加新的关系：

MATCH (m:Movie { title:“Cloud Atlas” })

MATCH (p:Person { name:“Tom Hanks” })

MERGE §-[r:ACTED_IN]->(m)

ON CREATE SET r.roles =[‘Zachry’]

RETURN p,r,m


添加新的节点和关系：

CREATE (y:Year { year:2014 })

MERGE (y)<-[:IN_YEAR]-(m10:Month { month:10 })

MERGE (y)<-[:IN_YEAR]-(m11:Month { month:11 })

RETURN y,m10,m11


条件选择

#1 WHERE

MATCH (m:Movie)

WHERE m.title = “The Matrix”

RETURN m

#2 WHERE

MATCH (p:Person)-[r:ACTED_IN]->(m:Movie)

WHERE p.name =~ “K.+” OR m.released > 2000 OR “Neo” IN r.roles

RETURN p,r,m

#3 NOT

MATCH (p:Person)-[:ACTED_IN]->(m)

WHERE NOT §-[:DIRECTED]->()

RETURN p,m

#4 ALIAS

MATCH (p:Person)

RETURN p, p.name AS name, toUpper(p.name), coalesce(p.nickname,“n/a”) AS nickname, { name: p.name,

label:head(labels§)} AS person

#5 COUNT

MATCH (:Person)

RETURN count(*) AS people

OR

RETURN count(DISTINCT role)

MATCH (actor:Person)-[:ACTED_IN]->(movie:Movie)<-[:DIRECTED]-(director:Person)

RETURN actor,director,count(*) AS collaborations

#6 ORDER

MATCH (a:Person)-[:ACTED_IN]->(m:Movie)

RETURN a,count(*) AS appearances

ORDER BY appearances DESC LIMIT 10;

#7 COLLECT

MATCH (m:Movie)<-[:ACTED_IN]-(a:Person)

RETURN m.title AS movie, collect(a.name) AS cast, count(*) AS actors

#8 UNION

MATCH (actor:Person)-[r:ACTED_IN]->(movie:Movie)

RETURN actor.name AS name, type® AS acted_in, movie.title AS title

UNION

MATCH (director:Person)-[r:DIRECTED]->(movie:Movie)

RETURN director.name AS name, type® AS acted_in, movie.title AS title

#9 WITH

MATCH (person:Person)-[:ACTED_IN]->(m:Movie)

WITH person, count(*) AS appearances, collect(m.title) AS movies

WHERE appearances > 1

RETURN person.name, appearances, movies

查询的结果可能是数字、字符串、或者列表、数组。