Question

我只是好奇在mongoose Query中.in（）和.all（）方法之间的区别是什么？你能用一个简单的例子来解释。

Answer 1

以下是mongodb.org的解释：

<强> $所有

$ all运算符类似于$ in，但不是匹配指定数组中的任何值，而是必须匹配数组中的所有值。例如，对象

{a：[1,2,3]}

将匹配

db.things.find（{a：{$ all：[2,3]}}）;

但不是

db.things.find（{a：{$ all：[2,3,4}}}）;

数组可以包含比$ all条件指定的元素更多的元素。 $ all指定必须匹配的最小元素集。

详细了解mongodb运算符here

Answer 2

$ all运算符检索包含我们传递的值子集的所有文档。子集可以是任何顺序。

$ in运算符检索包含我们传递的任一值的所有文档。

例如，考虑使用以下文档收集“技能”

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

db.skills.find（{技能：{$ all：[“烹饪”，“唱歌”]}}）将仅返回包含舞蹈和演唱技巧的文件，即Balaji和Ramesh。

db.skills.find（{技能：{$ in：[“烹饪”，“唱歌”]}}）`将返回所有文件，因为所有文件都包含烹饪或唱歌。

Answer 3

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-此数组运算符等效于AND操作。如果指定数组中的所有值都匹配，这将从集合中返回文档。以下内容可帮助您确定两者都具有“ Chess”，“ Cricket”价值的所有文档。

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

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

$ in-这是一个比较查询运算符，它基于列出可能条件的数组。它有助于查询各种值。它列出了查询中指定数组中存在的匹配 任何值的文档。以下内容有助于确定所有值为“ Chess”（棋）或“ C”（Cricket）
的文档

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

这将列出所有ObjectId的文档   7892de7a123be821ebcca757，7892de7a123be821ebcca758，   7892de7a123be821ebcca759和7892de7a123be821ebcca760

Answer 4

$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']},
]

.in（）和mongoose中的所有。（）运算符有什么区别？

4 个答案: