.mongoose中的.in()和.all()运算符有什么区别？

Question

我只是好奇mongoose查询中的.in()和.all()方法有什么区别？你能通过一个简单的例子来解释一下吗？

- Erik

Answer 1

$all运算符检索包含我们传递的值子集的所有文档。子集可以以任何顺序出现。

$in运算符检索包含我们传递的任一值的所有文档。

例如，考虑以下文档的“skills”集合：

{ "Name" : "Balaji", "skills" : [ "Dancing", "Cooking", "Singing" ] }
{ "Name" : "Ramesh", "skills" : [ "Cooking", "Singing" ] }
{ "Name" : "Suresh", "skills" : [ "Dancing", "Singing" ] }

db.skills.find（{skills：{$all：["烹饪"，"唱歌"]}}）将仅返回包含烹饪和唱歌技能的文档作为一组，即Balaji和Ramesh。

db.skills.find（{skills：{$in：["烹饪"，"唱歌"]}}）将返回所有文档，因为所有文档都包含烹饪或唱歌中的一个或多个技能。

- balajivijayan

Answer 2

以下是来自mongodb.org的说明：

$all

$all运算符类似于$in，但不同之处在于匹配指定数组中的所有值，而不仅仅是任意一个值。例如，对象

{ a: [ 1, 2, 3 ] }

将被以下查询所匹配

db.things.find( { a: { $all: [ 2, 3 ] } } );

但不会被以下查询所匹配

db.things.find( { a: { $all: [ 2, 3, 4 ] } } );

一个数组可以有比$all条件指定的元素更多。$all指定了必须匹配的最小元素集。

在这里阅读有关mongodb运算符的更多信息。

- udidu

Answer 3

$all - This an array operator that is equivalent to an $and operation.

[
    {name:'Shubham',hobbies:['cricket','dancing','football']},
    {name:'Chandrakesha',hobbies:['cricket','singing','dancing','football']},
    {name:'Nitish',hobbies:['cricket','singing','dancing','football']},
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

Query:->

{hobbies: { $all : ["readingbooks", "singing" ] } }
                OR
can write like below query
{ 
    $and: [
        {"hobbies": "readingbooks"},
        {"hobbies": "singing"},
    ]
}

will return only the documents which contains both readingbooks and singing hobbies

output:->

[
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

-------------------------------
$in operator retrieves all the documents which contains the either of the values we pass.

[
    {name:'Shubham',hobbies:['cricket','dancing','football']},
    {name:'Chandrakesha',hobbies:['cricket','singing','dancing','football']},
    {name:'Nitish',hobbies:['cricket','singing','dancing','football']},
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

Query:->

{hobbies: { $in : ["readingbooks", "singing" ] } }

                OR
can write like below query
{ 
    $or: [
        {"hobbies": "readingbooks"},
        {"hobbies": "singing"},
    ]
}

will return all the documents which contains any of them readingbooks or singing hobbies

output:->

[
    {name:'Chandrakesha',hobbies:['cricket','singing','dancing','football']},
    {name:'Nitish',hobbies:['cricket','singing','dancing','football']},
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

- Chandrakesha Rao

Answer 4

考虑以下集合“gamesapp”

{
   _id: ObjectId("7892de7a123be821ebcca757"),
   name: "kid1",
   games: [ "Chess", "Cricket", "Football", "Hockey", "Carrom" ],
   favourite_games: [ "Chess", "Cricket", "Football" ]
}

{
   _id: ObjectId("7892de7a123be821ebcca758"),
   name: "kid2",
   games: [ "Chess", "Cricket", "Football", "Hockey", "Carrom" ],
   favourite_games: [ "Chess", "Cricket" ]
}

{
   _id: ObjectId("7892de7a123be821ebcca759"),
   name: "kid3",
   games: [ "Chess", "Cricket", "Football", "Hockey", "Carrom" ],
   favourite_games: [ "Chess" ]
}

{
   _id: ObjectId("7892de7a123be821ebcca760"),
   name: "kid4",
   games: [ "Chess", "Cricket", "Football", "Hockey", "Carrom" ],
   favourite_games: [ "Chess", "Cricket" ]
}

$all - 这是一个数组操作符，相当于AND操作。如果指定的数组中匹配所有值，则应从集合中返回文档。以下有助于确定所有具有价值“Chess”“Cricket”的文档都。

db.gamesapp.find（{"favourite_games"：{$all：["Chess"，“Cricket”]}}）

这将列出ObjectId为7892de7a123be821ebcca757、7892de7a123be821ebcca758和7892de7a123be821ebcca760的文档

$in - 这是一种基于数组的比较查询运算符，列出可能的条件。它有助于查询各种值，列出与查询中指定的数组中存在的任何值匹配的文档。以下有助于确定所有具有价值'Chess' 或 'Cricket'的文档。

db.gamesapp.find({"favourite_games":{$in:["Chess", "Cricket"]}})

这将列出所有的文档，其ObjectId为7892de7a123be821ebcca757、7892de7a123be821ebcca758、7892de7a123be821ebcca759和7892de7a123be821ebcca760。该查询与“favourite_games”字段中包含“Chess”或“Cricket”的文档匹配。

- Karthik Balaguru