Neo4j Cypher syntax tutorial Entity, relationship addition, deletion and modification, advanced query

Neo4j example

After installing neo4j, visit the corresponding web page port and enter the following command to learn

node operation

create node

• Create a node labeled stu (label: classify data for easy management)

create(n:stu);// 这里的n就是随便起的一个变量名，代指当前实体或者关系，下文会使用到。

• Create a node with the label stu and the attribute value

create(n:stu{
    
    id:1,name:'小明',age:20});

query node

• Search by label

match (n:stu) return n; 
 // 上文说到 n类似变量名， 一般可用于后续操作，
 // match n:stu 指查询到标签为stu的节点 赋值给变量n ，return n则是将这批节点返回；

The running result is as shown in the figure below.

Neo4j uses the name attribute for display by default.

• Query by id

match (n:stu) where id(n) = 38023 return n;
//此id是neo4j默认分配给实体的id 不是上面定义的属性“id”

• Query by attribute

match (n:stu) where n.name = '小明' return n;

• Multi-attribute conditional query

match (n:stu) where n.name = '小明'and n.age = 20 and n.id = 1 return n;

edit entity

• Add multi-label

// neo4j 支持多标签
match (n:stu) where id(n) = 38023 set n:stu1 return n;
match (n:stu) where id(n) = 38023 set n:stu2 return n;

You can see that the node has three labels

• remove label

match (n:stu) where id(n) = 38023 remove n:stu2 return n;
match (n:stu) where id(n) = 38023 remove n:stu1 return n;

• modify a property

match (n:stu) where n.name='小明' set n.name = '小红' return n;

• Modify multiple attribute values

match (n:stu) where n.name='小红' set n.age = '200' set n.id = 2 return n;

You can see that the right side has been modified successfully

delete entity

//创建测试数据
create(n:stu{
    
    id:1,name:'小王',age:20});
//查询出来并删除
match (n:stu) where n.name = '小王' delete n;

If the deletion is successful, you can see a return prompt that an entity has been deleted

relational operations

Create new relationships and entities

This operation does not require an entity to be created in advance

//创建标签为stu 属性name 的两个实体、标签为test的关系一个 
create (n:stu{
    
    name:'小张'})-[r:test] -> (m:stu{
    
    name:'小李'})

//关系和实体同理  关系新建时也可以添加属性
create (n:stu{
    
    name:'小黄'})-[r:test{
    
    name:'夫妻'}] -> (m:stu{
    
    name:'小八'})

Note: Use match (n:stu) return n This command queries the entities and relationships of the stu tag

Existing Entity New Relationship

This operation requires the entity to be created in advance

// 这两行是一条命令   分割一下看的清晰  第一步就是查出来 m、n实体 第二布就是给他俩创建关系
match (n:stu),(m:stu) where n.name = '小李' and m.name = '小八' 
create (n)-[r:test{
    
    name:'儿子'}]->(m) ;

At this time, we can see that these four entities have been connected by matching

edit relationship

• modify properties

// 修改关系属性
match p = (n)-[r:test]->(m) where r.name='夫妻' set r.name='朋友';

// 我们想修改完后直接可以看到修改结果 我们在后面加一个return即可 将n-r-m赋值给一个变量 然后return这个变量 如下
match p = (n)-[r:test]->(m) where r.name='朋友' set r.name='闺蜜' return p;
//可以看到下放返回的不是提示信息 而是实体和关系 如下图

• relationship add property

// 直接set 新属性赋值即可 
match p = (n)-[r:test]->(m) where r.name='闺蜜' set r.color='红色' return p;

• Modify the label
  Note that neo4j does not support modifying the relationship label , so our operation of modifying the label is to recreate a relationship and delete the original relationship. This operation has no effect on use. It should be noted that the id of the relationship will change

// 四行是一条命令  第一行 搜出来想要修改的关系  第二行新建关系 第三行复制原属性  第四行删除原关系 
MATCH (n)-[r:test]->(m) where r.name='闺蜜'
CREATE (n)-[r2:relation]->(m)
SET r2 = r 
DELETE r

delete relationship

//直接match 锁定到某个或某几个关系 delete即可
match (n)-[r:relation]->(m) where r.name = '闺蜜' delete r;
//不确定的话 可以将delete换成return 先看一下返回的是不是要删的 然后再进行删除 命令如下
match p = (n)-[r:relation]->(m) where r.name = '闺蜜' return p;

Advanced Search

contains

//包含
match (n:stu) where n.name Contains '小' return n

starts with

//开始于某条件  类似 like 小%
match (n:stu) where n.name starts with '小' return n

ends with

//结束于某条件 类似 like %红
match (n:stu) where n.name ends with '红' return n

limit

//限制返回条数 放在最后使用 return 后面
match (n:stu) return n limit 2;

SKIP

// 跳过几条 然后返回
match (n:stu) return n skip 3;

paging

//limit 和skip组合使用就是分页
match (n:stu) return n skip 2 limit 2;

order by

• ascending order

//默认是升序 也可以加上 asc 效果一样 
// 注意 id(n) 这个写法只针对于 默认生成的id 如果是你添加的属性不可以这么写 
match(n:stu) return n order by id(n) ;

match(n:stu) return n order by id(n) asc;


//自己添加的属性要用 n.name 
match(n:stu) return n order by n.id asc;

• descending order

match(n:stu) return n order by n.id desc;

to be continued