Neo4j / Cypher-從匹配結果中獲取隨機節點

Question

我需要播種Neo4j數據庫。 假設添加了Person節點后，我需要它們編寫Book 。 這是我到目前為止的內容：

MATCH (p:Person)
WITH ["Book 1", "Book 2", "Book 3", "Book 4", "Book 5"] AS titles
UNWIND titles AS title
CREATE (???)-[:CREATED]->(:Content { title: title, content: "Words..." })

我以為我可以填寫??? 與來自p的隨機人MATCH ，這是第一行的MATCH 。 我怎樣才能做到這一點？

Answer 1

使用APOC程序，您可以使用函數從列表中選擇隨機項。 這是用法示例：

MATCH (p:Person)
WITH collect(p) as people
UNWIND ["Book 1", "Book 2", "Book 3", "Book 4", "Book 5"] AS title
WITH apoc.coll.randomItem(people) as person, title
CREATE (person)-[:CREATED]->(:Content { title: title, content: "Words..." })

Answer 2

如果您只想說5個不同的Person節點，而不必關心它們是否是隨機分布的，或者重復運行很可能獲得相同的節點，則可以使用此高效查詢（因為它不需要獲取所有Person節點）：

MATCH (p:Person)
WITH p LIMIT 5
WITH COLLECT(p) AS ps, ["Book 1", "Book 2", "Book 3", "Book 4", "Book 5"] AS titles
UNWIND [i IN RANGE(0, SIZE(ps)-1) | {p: ps[i], title: titles[i]}] AS data
WITH data.p AS p, data.title AS title
MERGE (p)-[:CREATED]->(:Content {title: title, content: "Words..."})

請注意，如果要重新運行此查詢，我將使用MERGE而不是CREATE來避免產生重復的關系和節點。