第四章 Mongodb聚合函数
插入 测试数据
for(var j=;j<;j++){
for(var i=1;i<3;i++){
var person={
Name:"jack"+i,
Age:i,
Address:["henan","wuhan"],
Course:[
{Name:"shuxue",Score:i},
{Name:"wuli",Score:i}
]
}
db.DemoTest.Person.insert(person)
}
}
Count
db.DemoTest.Person.count({Name:"jack1"})
返回数量
distinct
db.DemoTest.Person.distinct("Name")
返回不重复的Name值。
group
例子：按照Name分组，条件是Age大于46
db.DemoTest.Person.group({
"key":{"Name":true}, -----分组的keky
"initial":{"Person":[]},-------每组分享的一个”初始化函数“
"$reduce":function(cur,prev){ ------这个函数的第一个参数是当前的文档对象，第二个参数是上一次function操作的累计对象，第一次为initial中的{”person“：[]}。有多少个文档， $reduce就会调用多少次
prev.Person.push(cur);
},
"finalize":function(prev){ ---返回每组的数量
prev.count=prev.Person.length;
},
"condition":{"Age":{"$lt":46}} -----过滤条件
})
返回结果如下：
/* */
{
"0" : {
"Name" : "jack1",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9d6"),
"Name" : "jack1",
"Age" : 1,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 1
},
{
"Name" : "wuli",
"Score" : 1
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba07"),
"Name" : "jack1",
"Age" : 1,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 1
},
{
"Name" : "wuli",
"Score" : 1
}
]
}
],
"count" :
},
"" : {
"Name" : "jack2",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9d7"),
"Name" : "jack2",
"Age" : 2,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 2
},
{
"Name" : "wuli",
"Score" : 2
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba08"),
"Name" : "jack2",
"Age" : 2,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 2
},
{
"Name" : "wuli",
"Score" : 2
}
]
}
],
"count" :
},
"" : {
"Name" : "jack3",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9d8"),
"Name" : "jack3",
"Age" : 3,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 3
},
{
"Name" : "wuli",
"Score" : 3
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba09"),
"Name" : "jack3",
"Age" : 3,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 3
},
{
"Name" : "wuli",
"Score" : 3
}
]
}
],
"count" :
},
"" : {
"Name" : "jack4",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9d9"),
"Name" : "jack4",
"Age" : 4,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 4
},
{
"Name" : "wuli",
"Score" : 4
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba0a"),
"Name" : "jack4",
"Age" : 4,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 4
},
{
"Name" : "wuli",
"Score" : 4
}
]
}
],
"count" :
},
"" : {
"Name" : "jack5",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9da"),
"Name" : "jack5",
"Age" : 5,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 5
},
{
"Name" : "wuli",
"Score" : 5
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba0b"),
"Name" : "jack5",
"Age" : 5,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 5
},
{
"Name" : "wuli",
"Score" : 5
}
]
}
],
"count" :
},
"" : {
"Name" : "jack6",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9db"),
"Name" : "jack6",
"Age" : 6,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 6
},
{
"Name" : "wuli",
"Score" : 6
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba0c"),
"Name" : "jack6",
"Age" : 6,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 6
},
{
"Name" : "wuli",
"Score" : 6
}
]
}
],
"count" :
},
"" : {
"Name" : "jack7",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9dc"),
"Name" : "jack7",
"Age" : 7,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 7
},
{
"Name" : "wuli",
"Score" : 7
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba0d"),
"Name" : "jack7",
"Age" : 7,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 7
},
{
"Name" : "wuli",
"Score" : 7
}
]
}
],
"count" :
},
"" : {
"Name" : "jack8",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9dd"),
"Name" : "jack8",
"Age" : 8,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 8
},
{
"Name" : "wuli",
"Score" : 8
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba0e"),
"Name" : "jack8",
"Age" : 8,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 8
},
{
"Name" : "wuli",
"Score" : 8
}
]
}
],
"count" :
},
"" : {
"Name" : "jack9",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9de"),
"Name" : "jack9",
"Age" : 9,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 9
},
{
"Name" : "wuli",
"Score" : 9
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba0f"),
"Name" : "jack9",
"Age" : 9,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 9
},
{
"Name" : "wuli",
"Score" : 9
}
]
}
],
"count" :
},
"" : {
"Name" : "jack10",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9df"),
"Name" : "jack10",
"Age" : 10,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 10
},
{
"Name" : "wuli",
"Score" : 10
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba10"),
"Name" : "jack10",
"Age" : 10,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 10
},
{
"Name" : "wuli",
"Score" : 10
}
]
}
],
"count" :
},
"" : {
"Name" : "jack11",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e0"),
"Name" : "jack11",
"Age" : 11,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 11
},
{
"Name" : "wuli",
"Score" : 11
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba11"),
"Name" : "jack11",
"Age" : 11,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 11
},
{
"Name" : "wuli",
"Score" : 11
}
]
}
],
"count" :
},
"" : {
"Name" : "jack12",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e1"),
"Name" : "jack12",
"Age" : 12,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 12
},
{
"Name" : "wuli",
"Score" : 12
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba12"),
"Name" : "jack12",
"Age" : 12,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 12
},
{
"Name" : "wuli",
"Score" : 12
}
]
}
],
"count" :
},
"" : {
"Name" : "jack13",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e2"),
"Name" : "jack13",
"Age" : 13,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 13
},
{
"Name" : "wuli",
"Score" : 13
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba13"),
"Name" : "jack13",
"Age" : 13,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 13
},
{
"Name" : "wuli",
"Score" : 13
}
]
}
],
"count" :
},
"" : {
"Name" : "jack14",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e3"),
"Name" : "jack14",
"Age" : 14,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 14
},
{
"Name" : "wuli",
"Score" : 14
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba14"),
"Name" : "jack14",
"Age" : 14,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 14
},
{
"Name" : "wuli",
"Score" : 14
}
]
}
],
"count" :
},
"" : {
"Name" : "jack15",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e4"),
"Name" : "jack15",
"Age" : 15,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 15
},
{
"Name" : "wuli",
"Score" : 15
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba15"),
"Name" : "jack15",
"Age" : 15,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 15
},
{
"Name" : "wuli",
"Score" : 15
}
]
}
],
"count" :
},
"" : {
"Name" : "jack16",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e5"),
"Name" : "jack16",
"Age" : 16,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 16
},
{
"Name" : "wuli",
"Score" : 16
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba16"),
"Name" : "jack16",
"Age" : 16,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 16
},
{
"Name" : "wuli",
"Score" : 16
}
]
}
],
"count" :
},
"" : {
"Name" : "jack17",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e6"),
"Name" : "jack17",
"Age" : 17,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 17
},
{
"Name" : "wuli",
"Score" : 17
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba17"),
"Name" : "jack17",
"Age" : 17,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 17
},
{
"Name" : "wuli",
"Score" : 17
}
]
}
],
"count" :
},
"" : {
"Name" : "jack18",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e7"),
"Name" : "jack18",
"Age" : 18,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 18
},
{
"Name" : "wuli",
"Score" : 18
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba18"),
"Name" : "jack18",
"Age" : 18,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 18
},
{
"Name" : "wuli",
"Score" : 18
}
]
}
],
"count" :
},
"" : {
"Name" : "jack19",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e8"),
"Name" : "jack19",
"Age" : 19,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 19
},
{
"Name" : "wuli",
"Score" : 19
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba19"),
"Name" : "jack19",
"Age" : 19,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 19
},
{
"Name" : "wuli",
"Score" : 19
}
]
}
],
"count" :
},
"" : {
"Name" : "jack20",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9e9"),
"Name" : "jack20",
"Age" : 20,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 20
},
{
"Name" : "wuli",
"Score" : 20
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba1a"),
"Name" : "jack20",
"Age" : 20,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 20
},
{
"Name" : "wuli",
"Score" : 20
}
]
}
],
"count" :
},
"" : {
"Name" : "jack21",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9ea"),
"Name" : "jack21",
"Age" : 21,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 21
},
{
"Name" : "wuli",
"Score" : 21
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba1b"),
"Name" : "jack21",
"Age" : 21,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 21
},
{
"Name" : "wuli",
"Score" : 21
}
]
}
],
"count" :
},
"" : {
"Name" : "jack22",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9eb"),
"Name" : "jack22",
"Age" : 22,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 22
},
{
"Name" : "wuli",
"Score" : 22
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba1c"),
"Name" : "jack22",
"Age" : 22,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 22
},
{
"Name" : "wuli",
"Score" : 22
}
]
}
],
"count" :
},
"" : {
"Name" : "jack23",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9ec"),
"Name" : "jack23",
"Age" : 23,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 23
},
{
"Name" : "wuli",
"Score" : 23
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba1d"),
"Name" : "jack23",
"Age" : 23,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 23
},
{
"Name" : "wuli",
"Score" : 23
}
]
}
],
"count" :
},
"" : {
"Name" : "jack24",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9ed"),
"Name" : "jack24",
"Age" : 24,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 24
},
{
"Name" : "wuli",
"Score" : 24
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba1e"),
"Name" : "jack24",
"Age" : 24,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 24
},
{
"Name" : "wuli",
"Score" : 24
}
]
}
],
"count" :
},
"" : {
"Name" : "jack25",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9ee"),
"Name" : "jack25",
"Age" : 25,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 25
},
{
"Name" : "wuli",
"Score" : 25
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba1f"),
"Name" : "jack25",
"Age" : 25,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 25
},
{
"Name" : "wuli",
"Score" : 25
}
]
}
],
"count" :
},
"" : {
"Name" : "jack26",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9ef"),
"Name" : "jack26",
"Age" : 26,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 26
},
{
"Name" : "wuli",
"Score" : 26
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba20"),
"Name" : "jack26",
"Age" : 26,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 26
},
{
"Name" : "wuli",
"Score" : 26
}
]
}
],
"count" :
},
"" : {
"Name" : "jack27",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f0"),
"Name" : "jack27",
"Age" : 27,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 27
},
{
"Name" : "wuli",
"Score" : 27
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba21"),
"Name" : "jack27",
"Age" : 27,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 27
},
{
"Name" : "wuli",
"Score" : 27
}
]
}
],
"count" :
},
"" : {
"Name" : "jack28",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f1"),
"Name" : "jack28",
"Age" : 28,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 28
},
{
"Name" : "wuli",
"Score" : 28
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba22"),
"Name" : "jack28",
"Age" : 28,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 28
},
{
"Name" : "wuli",
"Score" : 28
}
]
}
],
"count" :
},
"" : {
"Name" : "jack29",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f2"),
"Name" : "jack29",
"Age" : 29,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 29
},
{
"Name" : "wuli",
"Score" : 29
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba23"),
"Name" : "jack29",
"Age" : 29,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 29
},
{
"Name" : "wuli",
"Score" : 29
}
]
}
],
"count" :
},
"" : {
"Name" : "jack30",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f3"),
"Name" : "jack30",
"Age" : 30,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 30
},
{
"Name" : "wuli",
"Score" : 30
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba24"),
"Name" : "jack30",
"Age" : 30,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 30
},
{
"Name" : "wuli",
"Score" : 30
}
]
}
],
"count" :
},
"" : {
"Name" : "jack31",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f4"),
"Name" : "jack31",
"Age" : 31,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 31
},
{
"Name" : "wuli",
"Score" : 31
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba25"),
"Name" : "jack31",
"Age" : 31,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 31
},
{
"Name" : "wuli",
"Score" : 31
}
]
}
],
"count" :
},
"" : {
"Name" : "jack32",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f5"),
"Name" : "jack32",
"Age" : 32,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 32
},
{
"Name" : "wuli",
"Score" : 32
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba26"),
"Name" : "jack32",
"Age" : 32,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 32
},
{
"Name" : "wuli",
"Score" : 32
}
]
}
],
"count" :
},
"" : {
"Name" : "jack33",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f6"),
"Name" : "jack33",
"Age" : 33,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 33
},
{
"Name" : "wuli",
"Score" : 33
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba27"),
"Name" : "jack33",
"Age" : 33,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 33
},
{
"Name" : "wuli",
"Score" : 33
}
]
}
],
"count" :
},
"" : {
"Name" : "jack34",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f7"),
"Name" : "jack34",
"Age" : 34,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 34
},
{
"Name" : "wuli",
"Score" : 34
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba28"),
"Name" : "jack34",
"Age" : 34,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 34
},
{
"Name" : "wuli",
"Score" : 34
}
]
}
],
"count" :
},
"" : {
"Name" : "jack35",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f8"),
"Name" : "jack35",
"Age" : 35,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 35
},
{
"Name" : "wuli",
"Score" : 35
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba29"),
"Name" : "jack35",
"Age" : 35,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 35
},
{
"Name" : "wuli",
"Score" : 35
}
]
}
],
"count" :
},
"" : {
"Name" : "jack36",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9f9"),
"Name" : "jack36",
"Age" : 36,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 36
},
{
"Name" : "wuli",
"Score" : 36
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba2a"),
"Name" : "jack36",
"Age" : 36,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 36
},
{
"Name" : "wuli",
"Score" : 36
}
]
}
],
"count" :
},
"" : {
"Name" : "jack37",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9fa"),
"Name" : "jack37",
"Age" : 37,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 37
},
{
"Name" : "wuli",
"Score" : 37
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba2b"),
"Name" : "jack37",
"Age" : 37,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 37
},
{
"Name" : "wuli",
"Score" : 37
}
]
}
],
"count" :
},
"" : {
"Name" : "jack38",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9fb"),
"Name" : "jack38",
"Age" : 38,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 38
},
{
"Name" : "wuli",
"Score" : 38
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba2c"),
"Name" : "jack38",
"Age" : 38,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 38
},
{
"Name" : "wuli",
"Score" : 38
}
]
}
],
"count" :
},
"" : {
"Name" : "jack39",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9fc"),
"Name" : "jack39",
"Age" : 39,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 39
},
{
"Name" : "wuli",
"Score" : 39
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba2d"),
"Name" : "jack39",
"Age" : 39,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 39
},
{
"Name" : "wuli",
"Score" : 39
}
]
}
],
"count" :
},
"" : {
"Name" : "jack40",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9fd"),
"Name" : "jack40",
"Age" : 40,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 40
},
{
"Name" : "wuli",
"Score" : 40
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba2e"),
"Name" : "jack40",
"Age" : 40,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 40
},
{
"Name" : "wuli",
"Score" : 40
}
]
}
],
"count" :
},
"" : {
"Name" : "jack41",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9fe"),
"Name" : "jack41",
"Age" : 41,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 41
},
{
"Name" : "wuli",
"Score" : 41
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba2f"),
"Name" : "jack41",
"Age" : 41,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 41
},
{
"Name" : "wuli",
"Score" : 41
}
]
}
],
"count" :
},
"" : {
"Name" : "jack42",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2b9ff"),
"Name" : "jack42",
"Age" : 42,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 42
},
{
"Name" : "wuli",
"Score" : 42
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba30"),
"Name" : "jack42",
"Age" : 42,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 42
},
{
"Name" : "wuli",
"Score" : 42
}
]
}
],
"count" :
},
"" : {
"Name" : "jack43",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2ba00"),
"Name" : "jack43",
"Age" : 43,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 43
},
{
"Name" : "wuli",
"Score" : 43
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba31"),
"Name" : "jack43",
"Age" : 43,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 43
},
{
"Name" : "wuli",
"Score" : 43
}
]
}
],
"count" :
},
"" : {
"Name" : "jack44",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2ba01"),
"Name" : "jack44",
"Age" : 44,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 44
},
{
"Name" : "wuli",
"Score" : 44
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba32"),
"Name" : "jack44",
"Age" : 44,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 44
},
{
"Name" : "wuli",
"Score" : 44
}
]
}
],
"count" :
},
"" : {
"Name" : "jack45",
"Person" : [
{
"_id" : ObjectId("54461dce69f872cf5ea2ba02"),
"Name" : "jack45",
"Age" : 45,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 45
},
{
"Name" : "wuli",
"Score" : 45
}
]
},
{
"_id" : ObjectId("54461dce69f872cf5ea2ba33"),
"Name" : "jack45",
"Age" : 45,
"Address" : [
"henan",
"wuhan"
],
"Course" : [
{
"Name" : "shuxue",
"Score" : 45
},
{
"Name" : "wuli",
"Score" : 45
}
]
}
],
"count" :
}
}
返回的json
mapReduce
mapReduce其实是一种编程模型，用在分布式计算中，其中有一个“map”函数，一个”reduce“函数。
map：
这个称为映射函数，里面会调用emit(key,value)，集合会按照你指定的key进行映射分组。
reduce：
这个称为简化函数，会对map分组后的数据进行分组简化，注意：在reduce(key,value)中的key就是
emit中的key，vlaue为emit分组后的emit(value)的集合，这里也就是很多{"count":1}的数组。
mapReduce:
这个就是最后执行的函数了，参数为map，reduce和一些可选参数。
在MongoDB存储的文档上执行聚合操作非常有用，这种方式的一个限制是聚合函数（比如，SUM、AVG、MIN、MAX）需要通过mapper和reducer函数来定制化实现。
MongoDB没有原生态的用户自定义函数（UDFs）支持。但是它允许使用db.system.js.save命令来创建并保存JavaScript函数，JavaScript函数可以在MapReduce中复用。
第一种统计方式--对应集合直接统计
1.在MongoDB javascript Shell中对Array对象进行了一些扩展，其中新增sum方法，以方便统计数据之用的。
Array.sum=function(arr){
if(arr.length == 0)
return null;
var s = arr[0];
for(var i = 1; i < arr.length; i++)
s += arr[i];
return s;
}
2.例子：按照名称分组，统计每组年龄的和，条件是年龄小于2.
如果统计数量：var map = function(){ emit(this.Name, 1); } 其实是让值永远为1
var map = function(){ emit(this.Name, this.Age); }
var reduce = function( key, values ){ return Array.sum(values); }
var options = {query: { Age: {$lt: 2} }, out: { inline : 1 }}
db.Person.mapReduce(map,reduce,options)
结果如下
/* */
{
"results" : [
{
"_id" : "jack1",
"value" : 2
}
],
"timeMillis" : ,
"counts" : {
"input" : 2,
"emit" : 2,
"reduce" : 1,
"output" : 1
},
"ok" : ,
"_o" : {
"results" : [
{
"_id" : "jack1",
"value" : 2
}
],
"timeMillis" : ,
"counts" : {
"input" : 2,
"emit" : 2,
"reduce" : 1,
"output" : 1
},
"ok" :
},
"_keys" : [
"results",
"timeMillis",
"counts",
"ok"
],
"_db" : {
"_mongo" : "connection to localhost:27017{ SSL: { sslSupport: false, sslPEMKeyFile: \"\" } }{ SSH: { host: \"\", port: 22, user: \"\", password: \"\", publicKey: { publicKey: \"\", privateKey: \"\", passphrase: \"\" }, currentMethod: } }",
"_name" : "local",
"system.indexes" : "local.system.indexes",
"prototype" : "local.prototype",
"startup_log" : "local.startup_log",
"TestCollection" : "local.TestCollection",
"TestCollection.Person" : "local.TestCollection.Person",
"DemoTest" : "local.DemoTest",
"DemoTest.Person" : "local.DemoTest.Person",
"system" : "local.system",
"system.js" : "local.system.js",
"mythings" : "local.mythings",
"age_totals" : "local.age_totals",
"Person" : "local.Person"
}
}
结果json
分析一下：
1. map部分
作用：用于分组的。
emit(param1, param2)
param1：需要分组的字段，this.字段名。
param2：需要进行统计的字段，this.字段名。
2. reduce部分
作用：处理需要统计的字段
var reduce = function(key, values){
......统计字段处理
}
key： 指分组字段（emit的param1）对应的值
values：指需要统计的字段（emit的param2）值组成的数组
简单介绍统计常用的方法：
* 对数值类型进行求和
var reduce = function(key, values){
return Array.sum(values);
}
* 对字符串类型进行拼凑
var reduce = function(key, values){
return values.join(', ');
}
3. options部分
{ query: { age: {$lt: 25} }, out: "name_totals" }
query：先筛选符合条件的记录出来，再进行分组统计。
out：将分组统计后的结果输出到哪个集合当中。
默认情况下，out所指定的集合在数据库断开连接后再次打开时，依旧存在，并保留之前的所有记录的。
4. 执行分组统计
>db.集合名.mapReduce( map, reduce, options )
第二种统计方式--命令统计
1.命令如下：
注意：out参数 out:"Person_Name" 代表会创建一个临时表Person_Name 然后再从临时表中查找，out:{inline:1} 代表直接显示在当前命令执行的结果中
var map = function(){ emit(this.Name, this.Age); }
var reduce = function( key, values ){ return Array.sum(values); }
db.runCommand({
mapreduce:"Person",
map:map,
reduce:reduce,
out:"Person_Name",
keeptemp: false,
query: { Age:{ $lt: 2 }},
sort:{ Name:1},
limit:3
})
解析：
mapreduce：
分组统计的集合名
eg：
mapreduce: 'mythings'
不能写成mapreduce: mythings，否则报异常：mythings is not defined
map,reduce ：
同上，不做阐述
out ：
将分组统计结果输出到某个集合。
注意：不能缺省，必须指定名称，否则报错，报错如下：
“exception: 'out' has to be a string or an object”
keeptemp ：
是否保留临时集合（指out指定的集合）
keeptemp：false时会在数据库断开连接后，MongoDB会移除该集合的所有记录。而不是删除。
keeptemp：true时即使数据库断开连接后，再次连接上，该临时集合依旧保持之前所有记录。
keeptemp默认值为true。
query ：
筛选记录后，再进行分组统计
eg:
query: { age:{ $lt: 25 }}
sort ：
对分组统计的集合进行排序，也即先排序，后再执行分组统计的。
注意：这里的排序需要用到索引，必须先创建索引。
limit ：
对分组统计的集合先进行限制返回记录的条数，然后再去进行统计操作。注意：不要理解成对统计后的结果进行限制返回记录条数。
verbose ：
显示时间统计信息，取值为true/false
参考资料
http://www.cnblogs.com/shanyou/archive/2012/08/05/2624073.html
http://www.52ij.com/jishu/3925.html
Mongodb学习笔记四(Mongodb聚合函数)的更多相关文章
-
Mongodb学习笔记一(Mongodb环境配置)
Mongodb学习 说明: MongoDB由databases组成,database由collections组成,collection由documents组成,document由fileds组成.Mo ...
-
MongoDB学习总结(三) —— 常用聚合函数
上一篇介绍了MongoDB增删改查命令的基本用法,这一篇来学习一下MongoDB的一些基本聚合函数. 下面我们直奔主题,用简单的实例依次介绍一下. > count() 函数 集合的count函数 ...
-
MongoDB学习笔记一(MongoDB介绍 + 基本指令 + 查询语句)
什么是MongoDB MongoDB 是由C++语言编写的,是一个基于分布式文件存储的开源数据库系统. 在高负载的情况下,添加更多的节点,可以保证服务器性能. MongoDB 旨在为WEB应用提供可扩 ...
-
MongoDb 学习笔记(一) --- MongoDb 数据库介绍、安装、使用
1.数据库和文件的主要区别 . 数据库有数据库表.行和列的概念,让我们存储操作数据更方便 . 数据库提供了非常方便的接口,可以让 nodejs.php java .net 很方便的实现增加修改删除功能 ...
-
MongoDB学习笔记(一) MongoDB介绍及安装（摘）
MongoDB是一个高性能,开源,无模式的文档型数据库,是当前NoSql数据库中比较热门的一种.它在许多场景下可用于替代传统的关系型数据库或键/值存储方式.Mongo使用C++开发.Mongo的官方网 ...
-
Mongodb学习笔记二(Mongodb基本命令)
第二章 基本命令 一.Mongodb命令 说明:Mongodb命令是区分大小写的,使用的命名规则是驼峰命名法. 对于database和collection无需主动创建,在插入数据时,如果databas ...
-
MongoDB学习笔记五：聚合
『count』count是最简单的聚合工具,返回集合中的文档数量:> db.foo.count()0> db.foo.insert({"x" : 1})> db. ...
-
MongoDB学习笔记四：索引
索引就是用来加速查询的.创建数据库索引就像确定如何组织书的索引一样.但是你的优势是知道今后做何种查询,以及哪些内容需要快速查找.比如:所有的查询都包括"date"键,那么很可能(至 ...
-
MongoDB学习笔记(四) 用MongoDB的文档结构描述数据关系
MongoDB的集合(collection)可以看做关系型数据库的表,文档对象(document)可以看做关系型数据库的一条记录.但两者并不完全对等.表的结构是固定的,MongoDB集合并没有这个约束 ...
随机推荐
-
oneM2M启动Release 3标准化，华为引领物联网技术布局
http://developer.huawei.com/cn/ict/news/cn/2016/06/onem2m [韩国,首尔,2016年6月] 国际权威的物联网组织oneM2M召开第23次技术全会 ...
-
ActiveMQ的几种集群配置
ActiveMQ是一款功能强大的消息服务器,它支持许多种开发语言,例如Java, C, C++, C#等等.企业级消息服务器无论对服务器稳定性还是速度,要求都很高,而ActiveMQ的分布式集群则能很 ...
-
C#下水晶报表打印自定义纸张
在VB6中,如果要自定义纸张很方便: Rpt.PaperSize = crPaperUser Rpt.SetUserPaperSize lZZG, lZZK 但在C#中却不行了,没有发现 SetU ...
-
RESTful架构
RESTful架构 1.什么是RESTful API设计原则 REST是Representational State Transfer的简写,意为“表现层状态转换” 是一种对资源状态进行操作的设计规则 ...
-
监听<;input/>;标签行为的方法总结
一.内容改变 1.<input onchange="javascript:function()"/>方法 onchange可以替换为下面几种:oninput,onpro ...
-
display属性
display 属性规定元素应该生成的框的类型. 值 描述 none 此元素不会被显示. block 此元素将显示为块级元素,此元素前后会带有换行符. inline 默认.此元素会被显示为内联元素,元 ...
-
javascript/ajax和php 进阶 之 项目实战
1,使用异步思想做一个下拉列表,能够选择和展示数据库中对应的信息. 1,事件知识:所有的事件可参照:https://www.jb51.net/html5/459444.html 2,js中this补充 ...
-
查看kubernets上的image信息
# 查看pods所使用的image kubectl describe pods $podsname -n $namespace #获取containers.$containername.image i ...
-
ACM-ICPC 2018 徐州赛区网络预赛 J Maze Designer(最大生成树，倍增lca)
https://nanti.jisuanke.com/t/31462 要求在一个矩形中任意选两个点都有唯一的通路,所以不会建多余的墙. 要求满足上述情况下,建墙的费用最小.理解题意后容易想到首先假设全 ...
-
centos启动zookeeper
切换到zookeeper的bin目录下,执行 ./zkServer.sh start