如果后续MATCH失败，来自WITH的Neo4j值将消失

Question

我遇到了这个问题，我有一个使用WITH

传递数据的密码

MATCH (u1:user {username: "pewpewlasers"}), (u2:user {username: "pewpew2"})
MERGE (u1)-[y:KNOWS]->(u2)
ON CREATE SET y.connected = 1
WITH y, has(y.connected) AS connected 
REMOVE y.connected
RETURN connected

这很有效。创建KNOWS关系后，connected为true其他false。因此，此密码返回true或false。现在我想扩展这个

MATCH (u1:user {username: "pewpewlasers"}), (u2:user {username: "pewpew2"})
MERGE (u1)-[y:KNOWS]->(u2)
ON CREATE SET y.connected = 1
WITH y, has(y.connected) AS connected 
REMOVE y.connected
WITH y, connected
MATCH (x)-[zz:LIKES]->(y)    <------------- this match
WITH zz, connected
RETURN zz, connected

现在connected仅在标记的匹配成功时才返回true或false。否则它会给出一个空的结果。无论connected是否成功，我都希望true返回false或MATCH。

修改

抱歉，我在第二个查询中遗漏了一些内容。

MATCH (u1:user {username: "pewpewlasers"}), (u2:user {username: "pewpew2"})
MERGE (u1)-[y:KNOWS]->(u2)
ON CREATE SET y.connected = 1
WITH y, has(y.connected) AS connected 
REMOVE y.connected
WITH y, connected
MATCH (x)-[zz:LIKES]->(y)    <------------- this match
MERGE x-[:LOVES]->(y)        <------------- EDIT
WITH zz, connected
RETURN zz, connected

在解决匹配问题时可选匹配，如果出现null错误，则会失败。有什么建议吗？

Answer 1

我认为这样的事情可能会成功。

MATCH (u1:user {username: "pewpewlasers"}), (u2:user {username: "pewpew2"})
MERGE (u1)-[y:KNOWS]->(u2)
ON CREATE SET y.connected = 1
WITH y, has(y.connected) AS connected 
REMOVE y.connected
WITH y, connected
OPTIONAL MATCH (x)-[zz:LIKES]->(yy)
FOREACH(ignoreMe IN CASE WHEN yy IS null THEN [] ELSE [1] END |
    MERGE x-[:LOVES]->(yy))
WITH zz, connected
RETURN zz, connected

OPTIONAL MATCH允许您保留所有初始行，然后您将为＆＃39; zz＆＃39;如果没有关系。