[英]Creating directed edges between nodes based on Time property in Neo4j
我是 Neo4j 和 Cypher 的新手,在將我們公司的關系數據庫轉換為基於圖形的模型時,我遇到了一個問題,我將不勝感激。
我的模型中有一個類型為 person 的節點,如下所示:
(:Person {Fname: 'John', catID: 1})
(:Person {Fname: 'George', catID: 2})
(:Person {Fname: 'Natalie', catID: 3})
......
我也有這樣的基於時間的類別節點:
(:Category {Id: 1, Date: '2015-02-05'})
(:Category {Id: 1, Date: '2015-01-05'})
(:Category {Id: 1, Date: '2015-03-10'})
(:Category {Id: 3, Date: '2014-03-10'})
(:Category {Id: 3, Date: '2015-05-10'})
......
現在我想創建從每個人到其類別中具有最小日期的節點的直接邊。 我在上面的例子中的意思是:
(:Person {Fname: 'John', catID: 1}) ---> (:Category {Id: 1, Date: '2015-01-05'})
(:Person {Fname: 'Natalie', catID: 3}) ---> (:Category {Id: 3, Date: '2014-03-10'})
之后,我想根據它們的 Date 屬性按升序在每個類別中的節點之間創建有向邊。 我的意思是:
(:Category {Id: 1, Date: '2015-01-05'}) ---> (:Category {Id: 1, Date: '2015-02-05'}) ---> (:Category {Id: 1, Date: '2015-03-10'})
(:Category {Id: 3, Date: '2014-03-10'}) ---> (:Category {Id: 3, Date: '2015-05-10'})
做這些事情所需的密碼是什么。 非常感謝提前
以下是您如何完成問題的第一部分,將人們附加到具有最短日期的相應類別節點:
MATCH (p:Person)
MATCH (c:Category)
WHERE p.catID = c.Id
WITH p, c
ORDER BY p.Fname, c.Date
WITH p, HEAD(COLLECT(c)) AS most_recent
MERGE (p)-[:IN_CATEGORY]->(most_recent)
現在我們可以這樣做:
MATCH (p:Person)-[:IN_CATEGORY]->(c:Category)
RETURN p.Fname, c.Date
我們得到了結果:
p.Fname c.Date
John 2015-01-05
Natalie 2014-03-10
要回答您的第二個問題,我們可以這樣做:
MATCH (c:Category) WITH c
ORDER BY c.Id, c.Date
WITH c.Id AS id,
COLLECT(c) AS categories,
COUNT(c) AS count
UNWIND range(1, count - 1) AS idx
WITH categories[idx - 1] AS from , categories[idx] AS to
CREATE (from)-[:NEXT]->(to);
我從邁克爾的回答中竊取了一些想法。 :) 您現在可以編寫這樣的查詢:
MATCH p = (:Person)-[:IN_CATEGORY]->(:Category)-[:NEXT*]->(:Category)
RETURN p
在此處查看成品: http : //console.neo4j.org/r/999rzg
這幾乎很簡單:)
MATCH (c:Category)
WITH c order by c.Date
// ordered list
WITH collect(c) as cats
// index for collection
UNWIND range(1,size(cats)-1) as idx
// subsequent entries
WITH cats[idx-1] as first, cats[idx] as second
CREATE (first)-[:NEXT]->(second)
RETURN count(*);
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