Question

我有一个用例，我试图通过使用Cypher中的RETURN CASE WHEN THEN子句来优化我的Neo4j db调用和代码，以根据WHEN结果运行不同的查询。这是我的示例：

MATCH (n {email: 'abc123@abc.com'}) 
RETURN  
CASE WHEN n.category='Owner' THEN  MATCH '(n)-[r:OWNS]->(m)'  
WHEN n.category='Dealer' THEN MATCH (n)-[r:SUPPLY_PARTS_FOR]->(m) 
WHEN n.category='Mechanic' THEN MATCH (n)-[r:SERVICE]-(m) END 
AS result;

我不确定这是否合法，但这是我想要实现的目标。我收到语法错误，例如无效的输入'>'。我怎样才能最好地做到这一点？编辑可能的APOC解决方案：这是我发现FOREACH局限性之前的计划。

MATCH (user:Person {email:{paramEmail}})
FOREACH (_ IN case when 'Owner' = {paramCategory} then [1] else [] end|
SET user:Owner, user += queryObj 
WITH user, {paramVehicles} AS coll
UNWIND coll AS vehicle
MATCH(v:Vehicles {name:vehicle}) 
CREATE UNIQUE (user)-[r:OWNS {since: timestamp()}]->(v)
SET r += paramVehicleProps 
)
FOREACH (_ IN case when 'Mechanic' = {Category} then [1] else [] end|
SET user:Owner, user += queryObj 
WITH user, {paramVehicles} AS coll
….
)
FOREACH (_ IN case when 'Dealer' = {paramCategory} then [1] else [] end|
SET user:Owner, user += queryObj 
WITH user, {paramVehicles} AS coll
…...

)
RETURN user,
CASE {paramCategory}

WHEN 'Owner' THEN [(n)-[r:OWNS]->(m) | m and r]
 WHEN 'Dealer' THEN [(n)-[r:SUPPLY_PARTS_FOR]->(m) | m] 
WHEN 'Mechanic' THEN [(n)-[r:SERVICE]-(m) | m]
 END AS result`,{
 paramQueryObj: queryObj,
 paramVehicles: makeVehicleArray,
 paramVehicleProps: vehiclePropsArray,
 paramSalesAgent: dealerSalesAgentObjarray,
 paramWarehouseAgent: dealerWarehouseAgentObjarray
}).....

有人知道要使用apoc.do.when（）转换吗？请注意，我在第一个THEN中需要输入'm'和'r'。

Answer 1

您仍应在第一次比赛中使用标签，否则将进行完整的数据库扫描，而不是通过电子邮件查找索引！

对于查询，您可以使用模式理解：

MATCH (n:Person {email: 'abc123@abc.com'}) 
RETURN  
CASE n.category 
WHEN 'Owner'    THEN  [(n)-[r:OWNS]->(m) | m]
WHEN 'Dealer'   THEN [(n)-[r:SUPPLY_PARTS_FOR]->(m) | m] 
WHEN 'Mechanic' THEN [(n)-[r:SERVICE]-(m) | m] END 
AS result;

如何在Neo4j Cypher中的CASE WHEN THEN子句中执行密码查询

1 个答案: