Cypher查询语言

[TOC] > [参考](https://zhuanlan.zhihu.com/p/88745411) ## 语法 ## 删除数据库 ``` MATCH (n) DETACH DELETE n ``` MATCH是匹配操作，而小括号()代表一个节点node（可理解为括号类似一个圆形），括号里面的n为标识符 ## 创建节点 **创建多人物个节点** ``` CREATE (n:Person {name:'John'}) RETURN n CREATE (n:Person {name:'Sally'}) RETURN n CREATE (n:Person {name:'Steve'}) RETURN n CREATE (n:Person {name:'Mike'}) RETURN n CREATE (n:Person {name:'Liz'}) RETURN n CREATE (n:Person {name:'Shawn'}) RETURN n ``` `CREATE`是**创建**操作，`Person`是**标签**，代表节点的类型。花括号{}代表节点的**属性**，属性类似Python的字典 **创建地区节点** ``` CREATE (n:Person {name:'Sally'}) RETURN n CREATE (n:Person {name:'Steve'}) RETURN n CREATE (n:Person {name:'Mike'}) RETURN n CREATE (n:Person {name:'Liz'}) RETURN n CREATE (n:Person {name:'Shawn'}) RETURN n ``` ## 创建关系 ``` MATCH (a:Person {name:'Shawn'}), (b:Person {name:'Sally'}) MERGE (a)-[:FRIENDS {since:2001}]->(b) // 创建更多 MATCH (a:Person {name:'Shawn'}), (b:Person {name:'John'}) MERGE (a)-[:FRIENDS {since:2012}]->(b) MATCH (a:Person {name:'Mike'}), (b:Person {name:'Shawn'}) MERGE (a)-[:FRIENDS {since:2006}]->(b) MATCH (a:Person {name:'Sally'}), (b:Person {name:'Steve'}) MERGE (a)-[:FRIENDS {since:2006}]->(b) MATCH (a:Person {name:'Liz'}), (b:Person {name:'John'}) MERGE (a)-[:MARRIED {since:1998}]->(b) ``` 创建 a->b 两个人的边,原因为 FRIENDS 创建人与地区的边 ``` MATCH (a:Person {name:'John'}), (b:Location {city:'Boston'}) MERGE (a)-[:BORN_IN {year:1978}]->(b) // 创建更多 MATCH (a:Person {name:'Liz'}), (b:Location {city:'Boston'}) MERGE (a)-[:BORN_IN {year:1981}]->(b) MATCH (a:Person {name:'Mike'}), (b:Location {city:'San Francisco'}) MERGE (a)-[:BORN_IN {year:1960}]->(b) MATCH (a:Person {name:'Shawn'}), (b:Location {city:'Miami'}) MERGE (a)-[:BORN_IN {year:1960}]->(b) MATCH (a:Person {name:'Steve'}), (b:Location {city:'Lynn'}) MERGE (a)-[:BORN_IN {year:1970}]->(b) ``` 创建后效果  ## 查询 查询下所有在Boston出生的人物 ``` MATCH (a:Person)-[:BORN_IN]->(b:Location {city:'Boston'}) RETURN a,b ```  查询所有对外有关系的节点 ``` MATCH (a)-->() RETURN a ```  查询所有有关系的节点 ``` MATCH (a)--() RETURN a ```  查询所有对外有关系的节点，以及关系类型 ``` MATCH (a)-[r]->() RETURN a.name, type(r) ```  查询所有有结婚关系的节点 ``` MATCH (n)-[:MARRIED]-() RETURN n ```  查找某人的朋友的朋友 ``` MATCH (a:Person {name:'Mike'})-[r1:FRIENDS]-()-[r2:FRIENDS]-(friend_of_a_friend) RETURN friend_of_a_friend.name AS fofName ```  ## 创建节点并建好关系 ``` CREATE (a:Person {name:'Todd'})-[r:FRIENDS]->(b:Person {name:'Carlos'}) ```  ## 增加/修改节点的属性 ``` MATCH (a:Person {name:'Liz'}) SET a.age=34 MATCH (a:Person {name:'Shawn'}) SET a.age=32 MATCH (a:Person {name:'John'}) SET a.age=44 MATCH (a:Person {name:'Mike'}) SET a.age=25 ``` ## 删除节点的属性 ``` MATCH (a:Person {name:'Mike'}) SET a.test='test' MATCH (a:Person {name:'Mike'}) REMOVE a.test ``` ## 删除节点 ``` MATCH (a:Location {city:'Portland'}) DELETE a ``` ## 删除有关系的节点 ``` MATCH (a:Person {name:'Todd'})-[rel]-(b:Person) DELETE a,b,rel ```