英文:
What is a correct way to update a property using Cypher?
问题
以下是翻译好的部分：
Query 1:
MATCH (p:Person)
WHERE p.name= "John"
SET p += {name: "Johan"};
Query 2:
MATCH (p:Person)
WHERE p.name= "John"
SET p.name="Johan";
I've run the PROFILE for both queries, and they are rather similar.
英文:
I have nodes that have first name. I want to update all of the names John to Johan. Is there a difference between this two queries? The end result seems the same to me.
Query 1
MATCH (p:Person)
WHERE p.name= "John"
SET p += {name: "Johan"};
Query 2
MATCH (p:Person)
WHERE p.name= "John"
SET p.name="Johan";
I've run the PROFILE for both queries, and they are rather similar.
PROFILE MATCH (p:Person) WHERE p.name= "John" SET p += {name: "Johan"};
PROFILE MATCH (p:Person) WHERE p.name= "John" SET p.name="Johan";
答案1
得分: 1
有一个“差异”，因为查询 1 使用 SetProperties 操作从地图中复制 所有 属性（该地图碰巧只有一个属性），而查询 2 使用 SetProperty 从文字中设置一个属性。
我认为使用 += 语法的最重要原因是当需要设置很多属性时。在这种情况下，编写：
SET p += x
比编写以下方式更容易（且不容易出错）：
SET p.a = x.a, p.b = x.b, p.c = x.c, ...
或者
SET p.a = 123, p.b = true, p.c = 'Fred', ...
特别是如果查询中的先前处理免费提供了 x。但即使必须创建 x 地图，结果更易阅读：
WITH p, {a: 123, b: true, c: 'Fred', ...} AS x
SET p += x
英文:
There certainly is a "difference", since Query 1 uses the SetProperties operation to copy all the properties from a map (that happens to have a single property), whereas Query 2 uses SetProperty to set a single property from a literal.
I think the most important reason for using the += syntax occurs when there are a lot of properties to be set. In that case, it is a lot easier (and less brittle) to write:
SET p += x
than:
SET p.a = x.a, p.b = x.b, p.c = x.c, ...
or
SET p.a = 123, p.b = true, p.c = 'Fred', ...
Especially if processing earlier in the query provides x for free. But even if you have to create the x map, the result is more readable:
WITH p, {a: 123, b: true, c: 'Fred', ...} AS x
SET p += x
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