SET

概述

SET语句用于更新或删除点、边的属性值。使用前，需先使用MATCH语句获取待修改的点、边数据。

注意：点、边的Schema（标签）无法修改。它们的系统属性（_id、_uuid、_from、_to、_from_uuid和_to_uuid）也无法修改。

示例图

CREATE GRAPH myGraph ANY

INSERT (rowlock:User {_id: "U01", name: "rowlock"}),
       (brainy:User {_id: "U02", name: "Brainy", gender: "male"}),
       (purplechalk:User {_id: "U03", name: "purplechalk", gender: "female"}),
       (mochaeach:User {_id: "U04", name: "mochaeach", gender: "female"}),
       (c:Club {_id: "C01"}),
       (rowlock)-[:Follows {createdOn: date("2024-01-05")}]->(brainy),
       (purplechalk)-[:Follows {createdOn: date("2024-02-01")}]->(brainy),
       (mochaeach)-[:Follows {createdOn: date("2024-02-10"}]->(brainy),
       (brainy)-[:Joins {memberNo: 1}]->(c)

更新属性

获取点n并更新其属性gender，获取边e并更新其属性createdOn：

MATCH (n:User {name: 'rowlock'})-[e:Follows]->(:User {name: 'Brainy'})
SET n.gender = 'male', e.createdOn = '2024-01-07'
RETURN n.gender, e.createdOn

结果：

删除属性

获取点n并删除属性gender的值：

MATCH (n:User {name: 'mochaeach'})
SET n.gender = null
RETURN n

Result: n

覆盖所有属性

获取点n并覆盖其全部属性，更新属性name并删除所有其他属性值：

MATCH (n:User {name: 'purplechalk'})
SET n = {name: 'MasterSwift'}
RETURN n

结果：n

删除所有属性

获取点n并删除其全部属性值：

MATCH (n:User {name: 'rowlock'})
SET n = {}
RETURN n

结果：n

使用CASE更新属性

根据Follows边的createdOn属性值，为其新属性weight设置值：

ALTER EDGE Follows ADD PROPERTY {weight UINT32}; 
MATCH ()-[e:Follows]->()
SET e.weight = CASE
  WHEN e.createdOn < '2024-01-31' THEN 10
  ELSE 8
END
RETURN e

结果：e

值类型不符

如果提供的值与属性值类型不同并且无法转换，将使用该属性值类型的默认值作为新值。

将边属性memberNo（UINT64类型）更新为一个字符串：

MATCH ()-[e:Joins]->()
SET e.memberNo = 'm2'
RETURN e

结果：e