MongoDB 数组查询

MongoDB在文档上支持数组，其次数组上可以实现嵌套，以及数组元素也可以文档。因此，对于文档上数组的操作，MongoDB提供很多种不同的方式，包括数组的查询，数组元素的添加删除等等。本文主要描述数组查询，供大家参考。

一、演示环境及数据

> db.version()        3.2.11        > db.users.insertMany(                  [                     {                       _id: 1,                       name: "sue",                       age: 19,                       type: 1,                       status: "P",                       favorites: { artist: "Picasso", food: "pizza" },                       finished: [ 17, 3 ],                       badges: [ "blue", "black" ],                       points: [                          { points: 85, bonus: 20 },                          { points: 85, bonus: 10 }                       ]                     },                     {                       _id: 2,                       name: "bob",                       age: 42,                       type: 1,                       status: "A",                       favorites: { artist: "Miro", food: "meringue" },                       finished: [ 11, 25 ],                       badges: [ "green" ],                       points: [                          { points: 85, bonus: 20 },                          { points: 64, bonus: 12 }                       ]                     },                     {                       _id: 3,                       name: "ahn",                       age: 22,                       type: 2,                       status: "A",                       favorites: { artist: "Cassatt", food: "cake" },                       finished: [ 6 ],                       badges: [ "blue", "red" ],                       points: [                          { points: 81, bonus: 8 },                          { points: 55, bonus: 20 }                       ]                     },                     {                       _id: 4,                       name: "xi",                       age: 34,                                type: 2,                                status: "D",                       favorites: { artist: "Chagall", food: "chocolate" },                       finished: [ 5, 11 ],                       badges: [ "red", "black" ],                       points: [                          { points: 53, bonus: 15 },                          { points: 51, bonus: 15 }                       ]                     },                     {                       _id: 5,                       name: "xyz",                       age: 23,                       type: 2,                       status: "D",                       favorites: { artist: "Noguchi", food: "nougat" },                       finished: [ 14, 6 ],                       badges: [ "orange" ],                       points: [                          { points: 71, bonus: 20 }                       ]                     },                     {                       _id: 6,                       name: "abc",                       age: 43,                       type: 1,                       status: "A",                       favorites: { food: "pizza", artist: "Picasso" },                       finished: [ 18, 12 ],                       badges: [ "black", "blue" ],                       points: [                          { points: 78, bonus: 8 },                          { points: 57, bonus: 7 }                       ]                     }                  ]                )

二、演示数组查询

1、数组元素模糊匹配

//如下示例，数组字段badges每个包含该元素black的文档都将被返回        > db.users.find({badges:"black"},{"_id":1,badges:1})        { "_id" : 1, "badges" : [ "blue", "black" ] }        { "_id" : 4, "badges" : [ "red", "black" ] }        { "_id" : 6, "badges" : [ "black", "blue" ] }

2、数组元素精确(全)匹配

//如下示例，数组字段badges的值为["black","blue"]的文档才能被返回(数组元素值和元素顺序全匹配)        > db.users.find({badges:["black","blue"]},{"_id":1,badges:1})        { "_id" : 6, "badges" : [ "black", "blue" ] }

3、通过数组下标返回指定的文档

数组的下标从0开始，指定下标值则返回对应的文档        //如下示例，返回数组badges中第一个元素值为black的文档        > db.users.find({"badges.1":"black"},{"_id":1,badges:1})        { "_id" : 1, "badges" : [ "blue", "black" ] }        { "_id" : 4, "badges" : [ "red", "black" ] }

4、范围条件任意元素匹配查询

//查询数组finished的元素值既大于15，又小于20的文档        > db.users.find( { finished: { $gt: 15, $lt: 20}},{"_id":1,finished:1})        { "_id" : 1, "finished" : [ 17, 3 ] }        { "_id" : 2, "finished" : [ 11, 25 ] }        { "_id" : 6, "finished" : [ 18, 12 ] }        //下面插入一个新的文档，仅包含单个数组元素        > db.users.insert({"_id":7,finished:[19]})        WriteResult({ "nInserted" : 1 })        //再次查询，新增的文档也被返回        > db.users.find( { finished: { $gt: 15, $lt: 20}},{"_id":1,finished:1})        { "_id" : 1, "finished" : [ 17, 3 ] }        { "_id" : 2, "finished" : [ 11, 25 ] }        { "_id" : 6, "finished" : [ 18, 12 ] }        { "_id" : 7, "finished" : [ 19 ] }

5、数组内嵌文档查询

//查询数组points元素1内嵌文档键points的值小于等于55的文档(精确匹配)        > db.users.find( { 'points.0.points': { $lte: 55}},{"_id":1,points:1})        { "_id" : 4, "points" : [ { "points" : 53, "bonus" : 15 }, { "points" : 51, "bonus" : 15 } ] }    //查询数组points内嵌文档键points的值小于等于55的文档，此处通过.成员的方式实现        > db.users.find( { 'points.points': { $lte: 55}},{"_id":1,points:1})        { "_id" : 3, "points" : [ { "points" : 81, "bonus" : 8 }, { "points" : 55, "bonus" : 20 } ] }        { "_id" : 4, "points" : [ { "points" : 53, "bonus" : 15 }, { "points" : 51, "bonus" : 15 } ] }

6、数组元素操作符$elemMatch

作用：数组值中至少一个元素满足所有指定的匹配条件        语法：  { <field>: { $elemMatch: { <query1>, <query2>, ... } } }        说明：  如果查询为单值查询条件，即只有<query1>，则无需指定$elemMatch        //如下示例,为无需指定$elemMatch情形        //查询数组内嵌文档字段points.points的值为85的文档        > db.users.find( { "points.points": 85},{"_id":1,points:1})        { "_id" : 1, "points" : [ { "points" : 85, "bonus" : 20 }, { "points" : 85, "bonus" : 10 } ] }        { "_id" : 2, "points" : [ { "points" : 85, "bonus" : 20 }, { "points" : 64, "bonus" : 12 } ] }        > db.users.find( { points:{ $elemMatch:{points:85}}},{"_id":1,points:1})        { "_id" : 1, "points" : [ { "points" : 85, "bonus" : 20 }, { "points" : 85, "bonus" : 10 } ] }        { "_id" : 2, "points" : [ { "points" : 85, "bonus" : 20 }, { "points" : 64, "bonus" : 12 } ] }        //单数组查询($elemMatch示例)        > db.scores.insertMany(        ... [{ _id: 1, results: [ 82, 85, 88 ] }, //Author : Leshami        ... { _id: 2, results: [ 75, 88, 89 ] }]) //Blog   : http://blog.csdn.net/leshami        { "acknowledged" : true, "insertedIds" : [ 1, 2 ] }        > db.scores.find({ results: { $elemMatch: { $gte: 80, $lt: 85 } } })        { "_id" : 1, "results" : [ 82, 85, 88 ] }        //数组内嵌文档查询示例($elemMatch示例)        //查询数组内嵌文档字段points.points的值大于等于70，并且bonus的值20的文档(要求2个条件都必须满足)        //也就是说数组points的至少需要一个元素同时满足以上2个条件，这样的结果文档才会返回        //下面的查询数组值{ "points" : 55, "bonus" : 20 }满足条件        > db.users.find( { points: { $elemMatch: { points: { $lte: 70 }, bonus: 20}}},{"_id":1,points:1})        { "_id" : 3, "points" : [ { "points" : 81, "bonus" : 8 }, { "points" : 55, "bonus" : 20 } ] }

7、数组元素操作符$all

作用：数组值中满足所有指定的匹配条件，不考虑多出的元素以及元素顺序问题        语法：{ <field>: { $all: [ <value1> , <value2> ... ] } }        > db.users.find({badges:{$all:["black","blue"]}},{"_id":1,badges:1})        { "_id" : 1, "badges" : [ "blue", "black" ] }  //此处查询的结果不考虑元素的顺序        { "_id" : 6, "badges" : [ "black", "blue" ] }  //只要包含这2个元素的集合都被返回        等价的操作方式        > db.users.find({$and:[{badges:"blue"},{badges:"black"}]},{"_id":1,badges:1})        { "_id" : 1, "badges" : [ "blue", "black" ] }        { "_id" : 6, "badges" : [ "black", "blue" ] }

8、数组元素操作符$size

作用：返回元素个数总值等于指定值的文档        语法：db.collection.find( { field: { $size: 2 } } );        说明：$size不支持指定范围，而是一个具体的值。此外针对$size，没有相关可用的索引来提高性能        //查询数组badges包含1个元素的文档               > db.users.find({badges:{$size:1}},{"_id":1,badges:1})        { "_id" : 2, "badges" : [ "green" ] }        { "_id" : 5, "badges" : [ "orange" ] }        //查询数组badges包含2个元素的文档        > db.users.find({badges:{$size:2}},{"_id":1,badges:1})        { "_id" : 1, "badges" : [ "blue", "black" ] }        { "_id" : 3, "badges" : [ "blue", "red" ] }        { "_id" : 4, "badges" : [ "red", "black" ] }        { "_id" : 6, "badges" : [ "black", "blue" ] }

9、数组元素操作符$slice

作用：用于返回指定位置的数组元素值的子集(是数值元素值得一部分，不是所有的数组元素值)        示例：db.collection.find( { field: value }, { array: {$slice: count } } );                //创建演示文档        > db.blog.insert(        ... {_id:1,title:"mongodb unique index",        ... comment: [        ... {"name" : "joe","content" : "nice post."},        ... {"name" : "bob","content" : "good post."},        ... {"name" : "john","content" : "greatly."}]}        ... )        WriteResult({ "nInserted" : 1 })        //通过$slice返回集合中comment数组第一条评论        > db.blog.find({},{comment:{$slice:1}}).pretty()        {                "_id" : 1,                "title" : "mongodb unique index",                "comment" : [                        {                                "name" : "joe",                                "content" : "nice post."                        }                ]        }        //通过$slice返回集合中comment数组最后一条评论        > db.blog.find({},{comment:{$slice:-1}}).pretty()        {                "_id" : 1,                "title" : "mongodb unique index",                "comment" : [                        {                                "name" : "john",                                "content" : "greatly."                        }                ]        }        //通过$slice返回集合中comment数组特定的评论(可以理解为分页)        //如下查询，返回的是第2-3条评论，第一条被跳过        > db.blog.find({},{comment:{$slice:[1,3]}}).pretty()        {                "_id" : 1,                "title" : "mongodb unique index",                "comment" : [                        {                                "name" : "bob",                                "content" : "good post."                        },                        {                                "name" : "john",                                "content" : "greatly."                        }                ]        }

10、$占位符，返回数组中第一个匹配的数组元素值(子集)

使用样式：                db.collection.find( { <array>: <value> ... },                                    { "<array>.$": 1 } )                db.collection.find( { <array.field>: <value> ...},                                    { "<array>.$": 1 } )        使用示例        > db.students.insertMany([                { "_id" : 1, "semester" : 1, "grades" : [ 70, 87, 90 ] },                { "_id" : 2, "semester" : 1, "grades" : [ 90, 88, 92 ] },                { "_id" : 3, "semester" : 1, "grades" : [ 85, 100, 90 ] },                { "_id" : 4, "semester" : 2, "grades" : [ 79, 85, 80 ] },                { "_id" : 5, "semester" : 2, "grades" : [ 88, 88, 92 ] },                { "_id" : 6, "semester" : 2, "grades" : [ 95, 90, 96 ] }])                                                  //通过下面的查询可知，仅仅只有第一个大于等于85的元素值被返回        //也就是说$占位符返回的是数组的第一个匹配的值，是数组的子集        > db.students.find( { semester: 1, grades: { $gte: 85 } },        ... { "grades.$": 1 } )        { "_id" : 1, "grades" : [ 87 ] }        { "_id" : 2, "grades" : [ 90 ] }        { "_id" : 3, "grades" : [ 85 ] }        > db.students.drop()        //使用新的示例数据        > db.students.insertMany([                { "_id" : 7, semester: 3, "grades" : [ { grade: 80, mean: 75, std: 8 },                                               { grade: 85, mean: 90, std: 5 },                                               { grade: 90, mean: 85, std: 3 } ] },            { "_id" : 8, semester: 3, "grades" : [ { grade: 92, mean: 88, std: 8 },                                               { grade: 78, mean: 90, std: 5 },                                               { grade: 88, mean: 85, std: 3 } ] }])        //下面的查询中，数组的元素为内嵌文档，同样如此，数组元素第一个匹配的元素值被返回        > db.students.find(        ...    { "grades.mean": { $gt: 70 } },        ...    { "grades.$": 1 }        ... )        { "_id" : 7, "grades" : [ { "grade" : 80, "mean" : 75, "std" : 8 } ] }        { "_id" : 8, "grades" : [ { "grade" : 92, "mean" : 88, "std" : 8 } ] }

三、小结
a、数组查询有精确和模糊之分，精确匹配需要指定数据元素的全部值
b、数组查询可以通过下标的方式进行查询
c、数组内嵌套文档可以通过.成员的方式进行查询
d、数组至少一个元素满足所有指定的匹配条件可以使用$elemMatch
e、数组查询中返回元素的子集可以通过$slice以及占位符来实现f、all满足所有指定的匹配条件，不考虑多出的元素以及元素顺序问题