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AQL 基本语法&用法

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ArangoDB查询语言（AQL）类似于结构化查询语言（SQL） 在它的目的。两者都支持读取和修改集合数据，但AQL不支持数据定义操作，例如创建和删除数据库，集合和索引。

虽然有些关键字重叠，但AQL语法与SQL不同。例如，SQL WHERE和AQL FILTER子句是等效的，因为它们都定义了返回结果的条件。但是，SQL使用预定义的序列来确定WHERE语句必须在哪里出现。在AQL中，子句从左到右执行，因此FILTER查询中子句的位置决定了它的优先级。

尽管有这些差异，任何具有SQL背景的人都应该没有学习AQL的困难。

ArangoDB

一、数据预览

本次使用的数据共有43条，每条数据包含姓氏、年龄、活动状态和特征等六个字段
ArangoDB

其中每个特征都有一个随机字母作为文档密钥。特质标签有英文和德文。
ArangoDB

地点由地名和经纬度组成：
ArangoDB

二、基本的CRUD

创建集合：

在创建文档之前，需要创造一个放置它的集合，集合可以通过Web界面，arangosh或驱动程序来创建。AQL无法创建集合。

ArangoDB

单击Web界面中的COLLECTIONS，然后单击Add Collection并键入 Charactersname。使用保存确认。新集合就出现在了列表中。

插入单个对象：

使用AQL插入文档
ArangoDB

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INSERT {
    "name": "Ned",
    "surname": "Stark",
    "alive": true,
    "age": 41,
    "traits": ["A","H","C","N","P"]
} INTO Characters

语法：

INSERT document INTO collectionName

该文档是一个对象，由属性键和值对组成。属性键的引号在AQL中是可选的。键总是字符串，而属性值可以有不同的类型：

  • null
  • boolean (true, false)
  • number (integer and floating point)
  • string
  • array
  • object

批量插入对象：

AQL不允许INSERT在单个查询中针对同一集合的多个操作。但是可以使用FOR循环体，插入多个文档。

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LET data = [
    { "name": "Robert", "surname": "Baratheon", "alive": false, "traits": ["A","H","C"] },
    { "name": "Jaime", "surname": "Lannister", "alive": true, "age": 36, "traits": ["A","F","B"] },
    { "name": "Catelyn", "surname": "Stark", "alive": false, "age": 40, "traits": ["D","H","C"] },
    { "name": "Cersei", "surname": "Lannister", "alive": true, "age": 36, "traits": ["H","E","F"] },
    { "name": "Daenerys", "surname": "Targaryen", "alive": true, "age": 16, "traits": ["D","H","C"] },
    { "name": "Jorah", "surname": "Mormont", "alive": false, "traits": ["A","B","C","F"] },
    { "name": "Petyr", "surname": "Baelish", "alive": false, "traits": ["E","G","F"] },
    { "name": "Viserys", "surname": "Targaryen", "alive": false, "traits": ["O","L","N"] },
    { "name": "Jon", "surname": "Snow", "alive": true, "age": 16, "traits": ["A","B","C","F"] },
    { "name": "Sansa", "surname": "Stark", "alive": true, "age": 13, "traits": ["D","I","J"] },
    { "name": "Arya", "surname": "Stark", "alive": true, "age": 11, "traits": ["C","K","L"] },
    { "name": "Robb", "surname": "Stark", "alive": false, "traits": ["A","B","C","K"] },
    { "name": "Theon", "surname": "Greyjoy", "alive": true, "age": 16, "traits": ["E","R","K"] },
    { "name": "Bran", "surname": "Stark", "alive": true, "age": 10, "traits": ["L","J"] },
    { "name": "Joffrey", "surname": "Baratheon", "alive": false, "age": 19, "traits": ["I","L","O"] },
    { "name": "Sandor", "surname": "Clegane", "alive": true, "traits": ["A","P","K","F"] },
    { "name": "Tyrion", "surname": "Lannister", "alive": true, "age": 32, "traits": ["F","K","M","N"] },
    { "name": "Khal", "surname": "Drogo", "alive": false, "traits": ["A","C","O","P"] },
    { "name": "Tywin", "surname": "Lannister", "alive": false, "traits": ["O","M","H","F"] },
    { "name": "Davos", "surname": "Seaworth", "alive": true, "age": 49, "traits": ["C","K","P","F"] },
    { "name": "Samwell", "surname": "Tarly", "alive": true, "age": 17, "traits": ["C","L","I"] },
    { "name": "Stannis", "surname": "Baratheon", "alive": false, "traits": ["H","O","P","M"] },
    { "name": "Melisandre", "alive": true, "traits": ["G","E","H"] },
    { "name": "Margaery", "surname": "Tyrell", "alive": false, "traits": ["M","D","B"] },
    { "name": "Jeor", "surname": "Mormont", "alive": false, "traits": ["C","H","M","P"] },
    { "name": "Bronn", "alive": true, "traits": ["K","E","C"] },
    { "name": "Varys", "alive": true, "traits": ["M","F","N","E"] },
    { "name": "Shae", "alive": false, "traits": ["M","D","G"] },
    { "name": "Talisa", "surname": "Maegyr", "alive": false, "traits": ["D","C","B"] },
    { "name": "Gendry", "alive": false, "traits": ["K","C","A"] },
    { "name": "Ygritte", "alive": false, "traits": ["A","P","K"] },
    { "name": "Tormund", "surname": "Giantsbane", "alive": true, "traits": ["C","P","A","I"] },
    { "name": "Gilly", "alive": true, "traits": ["L","J"] },
    { "name": "Brienne", "surname": "Tarth", "alive": true, "age": 32, "traits": ["P","C","A","K"] },
    { "name": "Ramsay", "surname": "Bolton", "alive": true, "traits": ["E","O","G","A"] },
    { "name": "Ellaria", "surname": "Sand", "alive": true, "traits": ["P","O","A","E"] },
    { "name": "Daario", "surname": "Naharis", "alive": true, "traits": ["K","P","A"] },
    { "name": "Missandei", "alive": true, "traits": ["D","L","C","M"] },
    { "name": "Tommen", "surname": "Baratheon", "alive": true, "traits": ["I","L","B"] },
    { "name": "Jaqen", "surname": "H'ghar", "alive": true, "traits": ["H","F","K"] },
    { "name": "Roose", "surname": "Bolton", "alive": true, "traits": ["H","E","F","A"] },
    { "name": "The High Sparrow", "alive": true, "traits": ["H","M","F","O"] }
]

FOR d IN data
    INSERT d INTO Characters

语法：

LET variableName = valueExpression

LET关键字定义了同名称的变量数据和对象值的数列，格式为[ {...}, {...}, ... ]

FOR variableName IN expression

用于迭代数据数组的每个元素 。在每个循环中，将一个元素分配给变量d。然后在INSERT语句中使用此变量。相当于下面的格式：

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INSERT {
    "name": "Robert",
    "surname": "Baratheon",
    "alive": false,
    "traits": ["A","H","C"]
} INTO Characters

INSERT {
    "name": "Jaime",
    "surname": "Lannister",
    "alive": true,
    "age": 36,
    "traits": ["A","F","B"]
} INTO Characters

...

检索

检索集合中的所有文档：

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FOR c IN Characters
    RETURN c

语法：

FOR variableName IN collectionName

对于集合中的每个文档，依次分配给变量c，然后根据循环体返回该文档。

选取其中一个文档如下：

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{
   "_key": "2861650",
   "_id": "Characters/2861650",
   "_rev": "_V1bzsXa---",
   "name": "Ned",
   "surname": "Stark",
   "alive": true,
   "age": 41,
   "traits": ["A","H","C","N","P"]
 },

该文档包含我们存储的四个属性，以及数据库系统添加的另外三个属性：

  • _key：文档键，用户可以在创建文档时提供文档键，也可以自动分配唯一值，不能改变，只读

  • _id：集合名/文档键，只读

  • _rev：系统管理的修订版ID，只读

检索特定文档：

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RETURN DOCUMENT("Characters", "2861650")
// --- or ---
RETURN DOCUMENT("Characters/2861650")

返回：

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[
  {
    "_key": "2861650",
    "_id": "Characters/2861650",
    "_rev": "_V1bzsXa---",
    "name": "Ned",
    "surname": "Stark",
    "alive": true,
    "age": 41,
    "traits": ["A","H","C","N","P"]
  }
]

语法：

DOCUMENT()

使用_key或_id检索特定文档，该函数还允许一次获取多个文档

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RETURN DOCUMENT("Characters", ["2861650", "2861653"])
// --- or ---
RETURN DOCUMENT(["Characters/2861650", "Characters/2861653"])

更新文档：

修改现有文件：

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UPDATE "2861650" WITH { alive: false } IN Characters
语法：
UPDATE documentKey WITH object IN collectionName

用列出的属性更新指定的文档（如果它们不存在则添加它们），但保持其余不变。要替换整个文档内容，则要使用REPLACE函数：

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REPLACE "2861650" WITH {
    name: "Ned",
    surname: "Stark",
    alive: false,
    age: 41,
    traits: ["A","H","C","N","P"]
} IN Characters

该函数也适用于循环，例如为所有文档添加新属性：

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FOR c IN Characters
    UPDATE c WITH { season: 1 } IN Characters

删除文件：

语法：

REMOVE _key IN Collectiosname

要从集合中完全删除文档，需要执行REMOVE操作。它的工作方式与其他修改操作类似，但没有WITH子句：

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REMOVE "2861650" IN Characters

三、匹配文件

语法：

FILTER

查找满足比_key相等更复杂的条件的文档，能够为要匹配的文档制定任意条件。

等于条件：

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FOR c IN Characters
    FILTER c.name == "Ned"
    RETURN c

过滤条件如下：“ 字符文档的属性name必须等于字符串Ned ”。如果条件适用，则返回字符文档。

范围条件：

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FOR c IN Characters
    FILTER c.age >= 13
    RETURN c.name

多种条件：

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FOR c IN Characters
    FILTER c.age < 13
    FILTER c.age != null
    RETURN { name: c.name, age: c.age }

//or

FOR c IN Characters
    FILTER c.age < 13 AND c.age != null
    RETURN { name: c.name, age: c.age }

替代条件：

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FOR c IN Characters
    FILTER c.name == "Jon" OR c.name == "Joffrey"
    RETURN { name: c.name, surname: c.surname }

四、排序和限制

限制语法：

LIMIT()

LIMIT后面跟着一个最大显示数的数字,限制结果显示行数。

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FOR c IN Characters
    LIMIT 5
    RETURN c.name

还可以使用LIMIT来跳过一定数量的记录返回下一个n个文档：

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FOR c IN Characters
    LIMIT 2, 5
    RETURN c.name

排序语法：

SORT()

DESC降序来反转排序顺序 

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FOR c IN Characters
    SORT c.name DESC
    LIMIT 10
    RETURN c.name

多个字段排序

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FOR c IN Characters
    FILTER c.surname
    SORT c.surname, c.name
    LIMIT 10
    RETURN {
        surname: c.surname,
        name: c.name
    }

此处FILTER的作用是仅保留surname为非空记录

五、组合

语法：
MERGE()

MERGE()的功能是将对象组合在一起。因为使用了原始字符属性{ traits: … }，所以后者被合并覆盖。

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FOR c IN Characters
    RETURN MERGE(c, { traits: DOCUMENT("Traits", c.traits)[*].en } )

六、图操作

创建图：

语法：

INSERT { _from: _id(A), _to: _id(B) } INTO ChildOf

实例：
首先，创建一个新的集合，并确保将集合类型更改为Edge。

ArangoDB

然后，通过查询多个集合的数据，将结果存入边集合中

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LET data = [                                                        //关系数据
    {
        "parent": { "name": "Ned", "surname": "Stark" },
        "child": { "name": "Robb", "surname": "Stark" }
    }, {
        "parent": { "name": "Ned", "surname": "Stark" },
        "child": { "name": "Sansa", "surname": "Stark" }
    }, {
        "parent": { "name": "Ned", "surname": "Stark" },
        "child": { "name": "Arya", "surname": "Stark" }
    }, {
        "parent": { "name": "Ned", "surname": "Stark" },
        "child": { "name": "Bran", "surname": "Stark" }
    }, {
        "parent": { "name": "Catelyn", "surname": "Stark" },
        "child": { "name": "Robb", "surname": "Stark" }
    }, {
        "parent": { "name": "Catelyn", "surname": "Stark" },
        "child": { "name": "Sansa", "surname": "Stark" }
    }, {
        "parent": { "name": "Catelyn", "surname": "Stark" },
        "child": { "name": "Arya", "surname": "Stark" }
    }, {
        "parent": { "name": "Catelyn", "surname": "Stark" },
        "child": { "name": "Bran", "surname": "Stark" }
    }, {
        "parent": { "name": "Ned", "surname": "Stark" },
        "child": { "name": "Jon", "surname": "Snow" }
    }, {
        "parent": { "name": "Tywin", "surname": "Lannister" },
        "child": { "name": "Jaime", "surname": "Lannister" }
    }, {
        "parent": { "name": "Tywin", "surname": "Lannister" },
        "child": { "name": "Cersei", "surname": "Lannister" }
    }, {
        "parent": { "name": "Tywin", "surname": "Lannister" },
        "child": { "name": "Tyrion", "surname": "Lannister" }
    }, {
        "parent": { "name": "Cersei", "surname": "Lannister" },
        "child": { "name": "Joffrey", "surname": "Baratheon" }
    }, {
        "parent": { "name": "Jaime", "surname": "Lannister" },
        "child": { "name": "Joffrey", "surname": "Baratheon" }
    }
]

FOR rel in data
    LET parentId = FIRST(                                    //FIRST()提取第一个元素
        FOR c IN Characters
            FILTER c.name == rel.parent.name                    //筛选条件
            FILTER c.surname == rel.parent.surname
            LIMIT 1
            RETURN c._id                                                 //返回_id
    )
    LET childId = FIRST(
        FOR c IN Characters
            FILTER c.name == rel.child.name
            FILTER c.surname == rel.child.surname
            LIMIT 1
            RETURN c._id
    )
    FILTER parentId != null AND childId != null                        //剔除_id都为空的记录
    INSERT { _from: childId, _to: parentId } INTO ChildOf       //将数据插入边集合
    RETURN NEW                                                                   //返回数据

也可以直接创建边数据：

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INSERT { _from: "Characters/robb", _to: "Characters/ned" } INTO ChildOf

遍历图：

语法：

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FOR v IN 1..1 OUTBOUND _id ChildOf

    RETURN v.name

其中1..1为遍历深度

实例：

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FOR c IN Characters
    FILTER c.name == "Bran"
    FOR v IN 1..1 OUTBOUND c ChildOf
        RETURN v.name

返回

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[
  "Ned",
  "Catelyn"
]

遍历的情况如下图：

ArangoDB

若是反向遍历，则需要使用到INBOUND关键字：

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FOR c IN Characters
    FILTER c.name == "Tywin"
    FOR v IN 2..2 INBOUND c ChildOf
        RETURN DISTINCT v.name
输出：

[
  "Joffrey"
]

遍历情况如下：

ArangoDB

需要注意的是，“1..1”限制了遍历深度为1，“2..2”限制了遍历深度为2，而”1..2”限制遍历深度既可以为1也可以为2。

七、地理空间查询

地点数据

创建地点集合：

ArangoDB

录入地点数据：

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LET places = [
    { "name": "Dragonstone", "coordinate": [ 55.167801, -6.815096 ] },
    { "name": "King's Landing", "coordinate": [ 42.639752, 18.110189 ] },
    { "name": "The Red Keep", "coordinate": [ 35.896447, 14.446442 ] },
    { "name": "Yunkai", "coordinate": [ 31.046642, -7.129532 ] },
    { "name": "Astapor", "coordinate": [ 31.50974, -9.774249 ] },
    { "name": "Winterfell", "coordinate": [ 54.368321, -5.581312 ] },
    { "name": "Vaes Dothrak", "coordinate": [ 54.16776, -6.096125 ] },
    { "name": "Beyond the wall", "coordinate": [ 64.265473, -21.094093 ] }
]

FOR place IN places
    INSERT place INTO Locations

设置地理空间索引：

在COLLECTIONS界面，添加新的Indexes，设置为coordinate字段：

ArangoDB

ArangoDB

查找附近的位置

语法：

NEAR()

找到最接近的坐标参考点

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FOR loc IN NEAR(Locations, 53.35, -6.26, 3)
    RETURN {
        name: loc.name,
        latitude: loc.coordinate[0],
        longitude: loc.coordinate[1]
    }

输出：

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[
  {
    "name": "Vaes Dothrak",
    "latitude": 54.16776,
    "longitude": -6.096125
  },
  {
    "name": "Winterfell",
    "latitude": 54.368321,
    "longitude": -5.581312
  },
  {
    "name": "Dragonstone",
    "latitude": 55.167801,
    "longitude": -6.815096
  }
]

查找半径内的位置

语法：

WITHIN()

从参考点搜索给定半径内的位置

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FOR loc IN WITHIN(Locations, 53.35, -6.26, 200 * 1000)
    RETURN {
        name: loc.name,
        latitude: loc.coordinate[0],
        longitude: loc.coordinate[1]
    }

输出

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[
  {
    "name": "Vaes Dothrak",
    "latitude": 54.16776,
    "longitude": -6.096125
  },
  {
    "name": "Winterfell",
    "latitude": 54.368321,
    "longitude": -5.581312
  }
]

按距离查找位置：

语法：

NEAR()或WITHIN()

通过添加一个可选的第五个参数返回到参考点的距离。必须是一个字符串：

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FOR loc IN NEAR(Locations, 53.35, -6.26, 3, "distance")
    RETURN {
        name: loc.name,
        latitude: loc.coordinate[0],
        longitude: loc.coordinate[1],
        distance: loc.distance / 1000
    }

输出：

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[
  {
    "name": "Vaes Dothrak",
    "latitude": 54.16776,
    "longitude": -6.096125,
    "distance": 91.56658640314431
  },
  {
    "name": "Winterfell",
    "latitude": 54.368321,
    "longitude": -5.581312,
    "distance": 121.66399816395028
  },
  {
    "name": "Dragonstone",
    "latitude": 55.167801,
    "longitude": -6.815096,
    "distance": 205.31879386198324
  }
]

使用AQL遇到的问题：

问题1：如何对查询结果进行计数并返回？

  • 解决方法：
1
RETURN COUNT(FOR v IN visitors FILTER v.ip == "127.0.0.1" RETURN 1)
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