Neo4j Cypher语法整理

• 查询John的朋友的朋友

添加5个人名节点，名字分别为

1CREATE (:People{name:"John"})
2CREATE (:People{name:"Joe"}) 
3CREATE (:People{name:"Sara"}) 
4CREATE (:People{name:"Steve"}) 
5CREATE (:People{name:"Maria"})

此时查询所有人的结果如下

match (people:People) return people

给这5个人添加上朋友关系

1MATCH (a:People{name:"John"}) MATCH (b:People{name:"Joe"}) CREATE (a) -[:friend]->(b)
2MATCH (a:People{name:"John"}) MATCH (b:People{name:"Sara"}) CREATE (a) -[:friend]->(b)
3MATCH (a:People{name:"Joe"}) MATCH (b:People{name:"Steve"}) CREATE (a) -[:friend]->(b)
4MATCH (a:People{name:"Sara"}) MATCH (b:People{name:"Maria"}) CREATE (a) -[:friend]->(b)

再次查询

match (people:People) return people

查询John朋友的朋友的名字

match (john {name:'John'})-[:friend]->()-[:friend]->(fof) return john.name,fof.name

结果

因为这里查询的只是名字，而不是节点，所以只会显示各自的名称。

• 给定一个用户名列表，找到名字在列表中的所有节点。匹配他们的朋友，仅返回那些他们关注的name属性以'S'开头的用户

  match (user)-[:friend]->(follower) where user.name in ['Joe','John','Sara','Maria','Steve'] and follower.name =~'S.*' return user.name,follower.name

结果

• 获取John和他的朋友数量

  match (n {name:'John'})-[:friend]->(friend) with n,count(friend) as friendsCount return n,friendsCount

• 获取John的朋友数量并保存为John的一个属性

  match (n {name:'John'})-[:friend]->(friend) with n,count(friend) as friendsCount set n.friendsCount=friendsCount return n.friendsCount

• 查询朋友的朋友，不包含自己

添加3个用户，两个好友关系

1create (adam:User {name:'Adam'}),(pernilla:User {name:'Pernilla'}),
2(david:User {name:'David'}),(adam)-[:friend]->(pernilla),
3(pernilla)-[:friend]->(david)

查询结果

match (n:User) return n

match (user {name:'Adam'})-[:friend]->()-[:friend]->(friend) return friend

match (user {name:'Adam'})-[:friend]->(friend),(friend)-[:friend]-(alluser) return alluser

 该方式也是不包含自己的，可以与下面包含自己的做出比较。

• 查询朋友的朋友，包含自己

  match (user {name:'Adam'})-[:friend]->(friend) match (friend)-[:friend]-(alluser) return alluser