Question

我在ArangoDB中有一个简单的父子关系。每个父文档可以包含零个到多个子级。假设父文档具有属性pa1，子文档具有一个属性ca1，并且引用返回到“_id_parent”的父_id。如何编写AQL查询以返回如下结果集：

    [{
            "_key": "111",
            "_id": "parent/111",
            "pa1": "aaa",
            "children": [{
                    "_key": "21",
                    "_id": "child/21",
                    "_id_parent": "parent/111",
                    "ca1": "www"
                },
                {
                    "_key": "22",
                    "_id": "child/22",
                    "_id_parent": "parent/111",
                    "ca1": "xxx"
                }
            ]
        },
        {
            "_key": "222",
            "_id": "parent/222",
            "pa1": "ddd",
            "children": [{
                    "_key": "31",
                    "_id": "child/31",
                    "_id_parent": "parent/222",
                    "ca1": "yyy"
                },
                {
                    "_key": "32",
                    "_id": "child/32",
                    "_id_parent": "parent/222",
                    "ca1": "zzz"
                }
            ]
        }
    ]

换句话说，我如何“扁平化”这个：

    FOR p IN Parent
    FILTER p.pa1 == @parm1
    LET children = (
        (FOR c IN Child
            FILTER c._id_parent == p._id
            RETURN c)
    )
    RETURN {p, children}

Answer 1

剩下要做的就是将儿童与父文件实际合并：

RETURN MERGE(p, {children})

这是RETURN MERGE(p, {children: children})的缩写形式。

p就是这样：

{
  "_id": "Parent/111",
  "_key": "111",
  "_rev": "_WLsUlK2--_",
  "pa1": "aaa"
}

{children}或更详细的{children: children}创建一个具有单个属性的对象，其名称为 children ，而children变量的值为：

{
  "children": [
    {
      "_key": "21",
      "_id": "Child/21",
      "_rev": "_WLsW4Su--_",
      "_id_parent": "Parent/111",
      "ca1": "www"
    },
    {
      "_key": "22",
      "_id": "Child/22",
      "_rev": "_WLsW8Zu--_",
      "_id_parent": "Parent/111",
      "ca1": "xxx"
    }
  ]
}

MERGE()结合了两个对象。由于属性键没有重叠（＆＃34; _id＆＃34;，＆＃34; _key＆＃34;，＆＃34; _rev＆＃34;，＆＃34; pa1＆＃34; vs.＆＃34;儿童＆＃34;），p的顶级属性不会被children取代。

BTW：您可以在子查询表达式周围留出一对括号 LET var = ( ( <subquery> ) ) - 只需LET var = ( <subquery> )即可。

ArangoDB AQL查询 - 将子项合并为父项

1 个答案: