测试数据

> var arr1 = ["aaaa", "bbbb", "cccc", "dddd"]; > var arr2 = ["eeee", "ffff", "gggg", "hhhh"]; > for (var i = 1; i <= 200; i++) { ...    db.user.insert( { x : i, y : [arr1[i%4], arr2[i%4]]} ) ... } WriteResult({ "nInserted" : 1 })

> db.user.findOne({x: 1}) {         "_id" : ObjectId("54ffb117e9ab791b5d8f85fe"),         "x" : 1,         "y" : [                 "bbbb",                 "ffff"         ] }

db.user.insert({x: 999, y:["a","b","c","d","e","f"], z:"zzzzzzzzzz"}); db.user.insert({x: 9999, y:[{a: 1}, {b: 2}], z:"zzzzzzzzzz"}); db.user.insert({x: 9999, y:[{a: 10}, {b: 20}], z:"zzzzzzzzzz"}); db.user.insert({x: 9999, y:[{a: 100}, {b: 200}], z:"zzzzzzzzzz"});

查询函数 db.集合名.find()

> db.user.find function ( query , fields , limit , skip, batchSize, options ){     var cursor = new DBQuery( this._mongo , this._db , this ,                         this._fullName , this._massageObject( query ) , fields , limit , skip , batchSize , options || this.getQueryOptions() );     var connObj = this.getMongo();     var readPrefMode = connObj.getReadPrefMode();     if (readPrefMode != null) {         cursor.readPref(readPrefMode, connObj.getReadPrefTagSet());     }     return cursor; }

查询条件

支持的条件

$eq   = $gt   > $gte  >= $lt   < $lte  <= $ne   <> $in   in $nin  not in

x大于188

y包含"gggg"

> db.user.find({x:{ $gt: 188}, y:"gggg"}) { "_id" : ObjectId("54ffb16de9ab791b5d8f86bb"), "x" : 190, "y" : [ "cccc", "gggg" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86bf"), "x" : 194, "y" : [ "cccc", "gggg" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86c3"), "x" : 198, "y" : [ "cccc", "gggg" ] }

x大于10，小于22

整个y数组是["bbbb", "ffff"]

同时按x倒序排序

输出前2行

> db.user.find({x:{ $lt: 22,   $lt: 10}, y:{ $all: ["bbbb", "ffff"]}}). sort({x: -1}). limit(2) { "_id" : ObjectId("54ffb117e9ab791b5d8f8606"), "x" : 9, "y" : [ "bbbb", "ffff" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8602"), "x" : 5, "y" : [ "bbbb", "ffff" ] }

$all也可以用下面的形式代替

> db.user.findOne({ y:["aaaa","eeee"]}); {         "_id" : ObjectId("54ffb117e9ab791b5d8f8601"),         "x" : 4,         "y" : [                 "aaaa",                 "eeee"         ] }

"in"条件

> db.user.find({x:{$lt: 10}, y:{ $in: ["aaaa", "ffff"]}}); { "_id" : ObjectId("54ffb117e9ab791b5d8f85fe"), "x" : 1, "y" : [ "bbbb", "ffff" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8601"), "x" : 4, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8602"), "x" : 5, "y" : [ "bbbb", "ffff" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8605"), "x" : 8, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8606"), "x" : 9, "y" : [ "bbbb", "ffff" ] }

“或”条件

找出x<5或者x>195的

> db.user.find({ $or:   [{x:{$lt:5}}, {x:{$gt:195}} ]}) { "_id" : ObjectId("54ffa67be9ab791b5d8f85fd"), "x" : 3 } { "_id" : ObjectId("54ffb117e9ab791b5d8f85fe"), "x" : 1, "y" : [ "bbbb", "ffff" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f85ff"), "x" : 2, "y" : [ "cccc", "gggg" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8600"), "x" : 3, "y" : [ "dddd", "hhhh" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8601"), "x" : 4, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86c1"), "x" : 196, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86c2"), "x" : 197, "y" : [ "bbbb", "ffff" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86c3"), "x" : 198, "y" : [ "cccc", "gggg" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86c4"), "x" : 199, "y" : [ "dddd", "hhhh" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f86c5"), "x" : 200, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("550154f11b048c7db6481552"), "x" : 999, "y" : [ "a", "b", "c", "d", "e", "f" ], "z" : "zzzzzzzzzz" } { "_id" : ObjectId("550158de3d7e7d39fc067da0"), "x" : 9999, "y" : [ { "a" : 10 }, { "b" : 20 } ], "z" : "zzzzzzzzzz" } { "_id" : ObjectId("550158f63d7e7d39fc067da1"), "x" : 9999, "y" : [ { "a" : 100 }, { "b" : 200 } ], "z" : "zzzzzzzzzz" } { "_id" : ObjectId("550158fc3d7e7d39fc067da2"), "x" : 9999, "y" : [ { "a" : 1 }, { "b" : 2 } ], "z" : "zzzzzzzzzz" }

查询嵌套文档

完整的

> db.obj.findOne() {         "_id" : ObjectId("5502a2ef773fc1f962baf14b"),         "name" : "obj1",         "arr" : [                 {                         "elemName" : "elem1",                         "elemValue" : 1                 },                 {                         "elemName" : "elem2",                         "elemValue" : 2                 }         ],         "subObj" : {                 "subName" : "subName1",                 "subArr" : [                         "subElem1",                         "subElem2",                         "subElem3"                 ]         } }

按subObj.subName查询。双引号不能省略。

> db.obj.find({ "subObj.subName":"subName1"}) { "_id" : ObjectId("5502a2ef773fc1f962baf14b"), "name" : "obj1", "arr" : [ { "elemName" : "elem1", "elemValue" : 1 }, { "elemName" : "elem2", "elemValue" : 2 } ], "subObj" : { "subName" : "subName1", "subArr" : [ "subElem1", "subElem2", "subElem3" ] } }

按subArr查询

> db.obj.find({"subObj.subArr":"subElem3"}) { "_id" : ObjectId("5502a2ef773fc1f962baf14b"), "name" : "obj1", "arr" : [ { "elemName" : "elem1", "elemValue" : 1 }, { "elemName" : "elem2", "elemValue" : 2 } ], "subObj" : { "subName" : "subName1", "subArr" : [ "subElem1", "subElem2", "subElem3" ] } }

用正则表达式做条件

找出y包含以多个A开头的元素的记录。正则表达式后面的i意思是不分大小写。

> db.user.find({y: { $regex:/^A+/,   $options:"i"}}).limit(1) { "_id" : ObjectId("54ffb117e9ab791b5d8f8601"), "x" : 4, "y" : [ "aaaa", "eeee" ] }

也可以简写成：

> db.user.find({y:   /^A+/i}).limit(1) { "_id" : ObjectId("54ffb117e9ab791b5d8f8601"), "x" : 4, "y" : [ "aaaa", "eeee" ] }

元素以a或A开头，同时不等于aaaa

> db.user.find({y: {$regex:/ ^A+  #A and a/, $options:" ix", $ne:"aaaa"}}).limit(1) { "_id" : ObjectId("550154f11b048c7db6481552"), "x" : 999, "y" : [ "a", "b", "c", "d", "e", "f" ], "z" : "zzzzzzzzzz" }

options包括：

i：不区分大小写

m：如果表达式有^xxx，或者xxx$，如果加上m，则/^x/和/x$/就能匹配aaa \nx和x \naaa这种带换行的情况。

x：让正则表达式可以注释。要用这个选项，必须在find里用$options:x的形式。

    例如

    > var   part  = "^A   #a and A";

s：让符号“.”能也能匹配新一行“\n”。必须在find里用$options:s的形式。

用代码方式自定义判断条件

> db.user.find({ $where: "this.x >= 100 && this.y[0] == 'aaaa'"}); { "_id" : ObjectId("54ffb117e9ab791b5d8f8661"), "x" : 100, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("54ffb16de9ab791b5d8f8665"), "x" : 104, "y" : [ "aaaa", "eeee" ] }

最无敌的方式是自己定义函数

> db.user.find({$where: ...   function() ...   { ...     if(this.y == null || this.y == undefined || this.y.length == 0) return false; ...     else if(this.x <= 10 && this.y[1] == 'eeee') return true; ...     else return false; ...   } ... }); { "_id" : ObjectId("54ffb117e9ab791b5d8f8601"), "x" : 4, "y" : [ "aaaa", "eeee" ] } { "_id" : ObjectId("54ffb117e9ab791b5d8f8605"), "x" : 8, "y" : [ "aaaa", "eeee" ] }

字段投影

不包含_id

> db.user.find({x:{$lt: 3}}, { _id: 0}) { "x" : 1, "y" : [ "bbbb", "ffff" ] } { "x" : 2, "y" : [ "cccc", "gggg" ] }

只显示x

> db.user.find({x:{$lt: 3}}, { x:1, _id:0}) { "x" : 1 } { "x" : 2 }

除了x，其它的都显示

> db.user.find({x:{$lt: 3}}, {x:0, _id: 0}) { "y" : [ "bbbb", "ffff" ] } { "y" : [ "cccc", "gggg" ] }

投影里除了_id以外，要么全是1，要么全是0，否则就报错

> db.user.find({x:{$lt: 3}}, {x:0, y:1}) Error: error: {         "$err" : "Can't canonicalize query: BadValue Projection   cannot have a mix of inclusion and exclusion.",         "code" : 17287 }

对于数组，用$slice控制只返回前几个元素还是后几个元素

返回前面数第一个元素

> db.user.find({x:{$lt: 3}}, {y: { $slice: 1}, x:0, _id: 0}) { "y" : [ "bbbb" ] } { "y" : [ "cccc" ] } 返回后面数第一个元素  > db.user.find({x:{$lt: 3}}, {y: {$slice:   -1}, x:0, _id: 0}) { "y" : [ "ffff" ] } { "y" : [ "gggg" ] }

$slice后面跟数组，可以灵活控制返回哪些数据

先看完整数组

> db.user.find( {x: 999}, {y:1, _id:0}) { "y" : [   "a", "b", "c", "d", "e", "f"  ] }

如果从前面数，就是从0开始，[2,2]的意思是从第3个元素开始，返回2个元素

> db.user.find( {x: 999}, { y: { $slice: [ 2,2]}, _id:0, x:0, z:0} ) { "y" : [   "c", "d"  ] }

如果是从后面数，就是从-1开始，[-3,2]就是从倒数第3个开始，返回2个元素。 > db.user.find( {x: 999}, { y: { $slice: [ -3,2]}, _id:0, x:0, z:0} ) { "y" : [   "d", "e"  ] }

过滤数组里的文档元素

先看完整的

> db.user.find({x:9999}, {z:0, _id:0}).sort({y: 1}) { "x" : 9999, "y" : [ { "a" : 1 }, { "b" : 2 } ] } { "x" : 9999, "y" : [ { "a" : 10 }, { "b" : 20 } ] } { "x" : 9999, "y" : [ { "a" : 100 }, { "b" : 200 } ] }

只显示包含{a:10}的y

> db.user.find({x:9999}, {y:{ $elemMatch:{a:10}}, z:0, _id:0}) { "x" : 9999,   "y" : [ { "a" : 10 } ]  } { "x" : 9999 } { "x" : 9999 }