Neo4j，匹配关系 WHERE AND

Question

您好，我正在尝试使用“WHERE AND”来匹配 Neo4j 关系

我的示例关系是:“用户访问国家/地区”

我是这样创建的...

MATCH (c:Country{Name:Country}) MERGE (u:User{Email:Email,UserID: UserID}) MERGE (u)-[r:Visits]->(c)
//Countries are previously created and Users may or may not exist

然后我查询(This Works):

MATCH (u:User)-[r:Visits]->(c:Country) where c.Name='France' or c.Name='Spain' return u

结果:显示所有访问过西类牙或法国的用户，即使他们只访问过两个国家之一。

但是我试图做的是完全相同的查询，但使用“AND”而不是“OR”。我可以在其中获得访问过“法国”和“西类牙”的用户。

MATCH (u:User)-[r:Visits]->(c:Country) where c.Name='France' AND c.Name='Spain' return u

结果:找到 0 个节点和关系..

我能做什么？

Answer 1

在您的查询中，您匹配单个国家/地区节点并说该节点的名称必须是 France并且必须是 Spain .

您想要的是找到所有访问过法国和西类牙的用户。有几种方法可以走...

//match both countries against the same user and identify them separtely
//making two matches in a single query
MATCH (u:User)-[:VISITS]->(c1:Country), (u)-[:VISITS]->(c2:Country)
WHERE c1.name = "France"
AND c2.name = "Spain"
RETURN u.name

//match all users that have been to either and only return the one that have been to both
MATCH (u:User)-[r:VISITS]->(c:Country) 
WHERE (c.name IN [ "France", "Spain"])
WITH u, count(*) AS num
WHERE num = 2
RETURN u.name, num 

它认为第一更好，因为它更精确，可能更有效。