Question

我正在将Neo4j 3.5.2 Desktop与Nodejs一起使用。我正在尝试更新用户记录属性，并在同一查询中添加/删除与其他节点的关系：我的查询如下：

 MATCH (user:Dealer {email: $paramObj.email})
 SET user += apoc.map.clean($paramObj, ["email","vehicles"],[])
                    WITH user, $paramObj.vehicles AS vehicles
                    UNWIND vehicles AS vehicle
                    MATCH(v:Vehicles {name:vehicle}) 
                    MERGE (user)-[r:SUPPLY_PARTS_FOR]->(v)
                    ON CREATE SET  r.since = timestamp()
                    WITH vehicles,user
                    MATCH (user)-[r:SUPPLY_PARTS_FOR]->(v)
                    WHERE NOT apoc.coll.contains(vehicles,v.name)
                    DELETE r
                    WITH $paramObj.email AS dealeremail
                    MATCH (user:Dealer {email: dealeremail})
                    RETURN user

我遇到的问题是，当与删除车辆关系（r）有关的查询导致零行时，返回空的“用户”数组。

如何保留原始的“用户”结果或保存电子邮件地址以重做查询。我尝试将WITH $ paramObj.email作为DealerEmail使用，但似乎无法转发DealerEmail ...可以。

Answer 1

此问题是由于返回零行导致的，所以我想到OPTIONAL MATCH也将返回NULL结果，但只有一行具有空值。因此，我更改了“匹配”以搜索要删除的关系，并将其更改为“可选匹配”。

  MATCH (user:Dealer {email: $paramObj.email})
  SET user += apoc.map.clean($paramObj, ["email","vehicles"],[])
                        WITH user, $paramObj.vehicles AS vehicles
                        UNWIND vehicles AS vehicle
                        MATCH(v:Vehicles {name:vehicle}) 
                        MERGE (user)-[r:SUPPLY_PARTS_FOR]->(v)
                        ON CREATE SET  r.since = timestamp()
                        WITH vehicles,user
                        OPTIONAL MATCH (user)-[r:SUPPLY_PARTS_FOR]->(v)
                        WHERE NOT apoc.coll.contains(vehicles,v.name)
                        DELETE r
                        RETURN user

这成功了

在Neo4j Cypher中在查询期间保留查询结果

1 个答案: