Cypher Query：当value为null时，如何使用文字映射语法

Question

我正在尝试使用COLLECT函数来构造使用文字映射语法的对象数组。但是，如果我使用的属性没有返回值，我宁愿返回一个空数组，而不是数组的对象元素保留其属性的空值。如何忽略这些值并返回[]而不是这个？

[
   {
      property_a: null,
      property_b: null
   }
]

这是我尝试过的密码查询：

MATCH (n)-[r]-()
WHERE n.id={_nodeid}
WITH n
OPTIONAL MATCH (n)-[instantiationlist:INSTANTIATES]->(target)
WITH n, COLLECT({
        container : instantiationlist.container,
        target    : target.id
    }) AS instantiationset
RETURN n.id AS id, 
       n.name                 AS name, 
       n.color                AS color,
       n.background           AS background,
       LABELS(n)[0]           AS type,
       instantiationset       AS instantiations;

我正在尝试为实例化集设置值[]而不是：

[
    {
      "container": null,
      "target": null
    }
]

Answer 1

此查询应该有效。

OPTIONAL MATCH (n {id: 123})-[ilist:INSTANTIATES]->(target)
WITH n, COLLECT(
  CASE
    WHEN ilist.container IS NULL THEN NULL
    ELSE { container : ilist.container, target : target.id } END
) AS iset
RETURN n.id AS id, n.name AS name, n.color AS color, n.background AS background, LABELS(n)[0] AS type, iset AS instantiations;