Orientdb SubQuery Max Date

Posted 2021-04-07

我搜索过这个并没有太多运气。我在OrientDb（3.0.2）中有一个图形数据库设置，并且我遇到了一些subquerys的问题。我可以在经典的关系数据库中轻松编写。我玩过LET和$ parent / $ children，但这些概念仍然有点令人困惑。

三个顶点：实体< - 检查 - >违规

我希望每个实体的最后一次检查（日期），并知道有多少违规与该检查相关联。

我知道如何为每次检查提取违规数量（边缘的大小（））。我也知道如何拉动每个实体的最大检验日期，但将这两个实体结合起来是一件很困难的事情。有什么想法吗？谢谢！

更新：我想我越来越接近，但仍然不确定如何进行“内部”联接。不确定我是否完全理解$ parent / $ current变量的工作原理。此查询不起作用

SELECT
    entityId
    ,$a.num_violations
    ,max(Date) as mDate
FROM (
    SELECT
        @rid AS entityId
        ,in('COMPLETED_AT').Date as Date
    FROM Entity
    unwind Date
)
let $a = (
  SELECT
    Date
    ,out('FOUND_DURING').size() as num_violations
  FROM Inspection
  WHERE $parent.mDate = Date
  AND $parent.entityId in out('COMPLETED_AT').@rid
)
GROUP BY entityId
    ,$a.num_violations

答案

试试这个：

select expand($c)
let $a = (select date, out("link")[@class="Violations"].size() as num_violations from Inspection),
$b = (select name, max(date) as max_date from (select name, in("link").date as date from Entity unwind date) group by name),
$c = unionAll($a, $b)

这就是你得到的：

+----+-------------------+--------------+----------+-------------------+
|#   |date               |num_violations|name      |max_date           |
+----+-------------------+--------------+----------+-------------------+
|0   |2018-08-31 00:00:00|1             |          |                   |
|1   |2018-08-30 00:00:00|2             |          |                   |
|2   |2018-08-29 00:00:00|1             |          |                   |
|3   |                   |              |entity_001|2018-08-31 00:00:00|
|4   |                   |              |entity_002|2018-08-29 00:00:00|
+----+-------------------+--------------+----------+-------------------+

UPDATE

select expand($c)
let $a = (select name as entity_name, max(date) as max_date from (select name, in("link").date as date from Entity unwind date) group by name),
$b = (select out("link")[@class="Violations"].size() as num_violations from Inspection),
$c = unionAll($a, $b)


+----+-----------+-------------------+--------------+
|#   |entity_name|max_date           |num_violations|
+----+-----------+-------------------+--------------+
|0   |entity_001 |2018-08-31 00:00:00|              |
|1   |entity_002 |2018-08-29 00:00:00|              |
|2   |           |                   |1             |
|3   |           |                   |2             |
|4   |           |                   |1             |
+----+-----------+-------------------+--------------+

希望能帮助到你

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