链式查询

db.person.find().limit(4).sort({sex:-1}) // sort来说，1 是升序， -1 是降序
尽量不要用mongodb去做一些复杂的运算

分页的写法

···
最简单的分页的写法
var page1 = db.person.find(name).limit(100);
var page2 = db.person.find(name).skip(100).limit(100);
···

指定选中的列保留

db.str.find({},{_id:0,age:1}); //查询出age，不要_id

大于小于等于

> var cond={"age":{"$gte":1,"$lte":2}}
> db.person.find(cond)
{ "_id" : ObjectId("56760f3c5001a3b4af601567"), "name" : "hxc19", "age" : 1 }
{ "_id" : ObjectId("56760f3c5001a3b4af601568"), "name" : "hxc20", "age" : 1.0526315789473684 }

in,nin,or in,nin:一个key后再加上一个子文档。

> var cond={"age":{"$in":[1,2,3,4]}}
> db.person.find(cond)
{ "_id" : ObjectId("56760f3c5001a3b4af601567"), "name" : "hxc19", "age" : 1 }

find中的正则表达式，和sql中的like操作一个样 O(N) Table Scan

> var cond={"name":/18$/}
> db.person.find(cond)
{ "_id" : ObjectId("56760f3c5001a3b4af601566"), "name" : "hxc18", "age" : 0.9473684210526315 }

查询数组中的元素

> var single={"name":"jack",address:["anhui","shanghai","beijing"]}
> db.mytest.insert(single)
> db.mytest.find()
{ "_id" : ObjectId("567632624163f2ea4dd06e96"), "name" : "jack", "address" : [  "anhui",  "shanghai",  "beijing" ] }
> db.mytest.find({"address":"anhui"})
{ "_id" : ObjectId("567632624163f2ea4dd06e96"), "name" : "jack", "address" : [  "anhui",  "shanghai",  "beijing" ] }

all操作

db.mytest.find({"address":{"$all":["anhui","shanghai"]}})
{ "_id" : ObjectId("567632624163f2ea4dd06e96"), "name" : "jack", "address" : [  "anhui",  "shanghai",  "beijing" ] }
db.mytest.find({"address":{"$all":["anhui","s"]}})

size操作

db.mytest.find({"address":{"$size":2}})
db.mytest.find({"address":{"$size":3}})
{ "_id" : ObjectId("567632624163f2ea4dd06e96"), "name" : "jack", "address" : [  "anhui",  "shanghai",  "beijing" ] }

slice操作

db.mytest.find({"name":"jack"},{"address":{"$slice":1}})
{ "_id" : ObjectId("567632624163f2ea4dd06e96"), "name" : "jack", "address" : [  "anhui" ] }
db.mytest.find({"name":"jack"},{"address":{"$slice":2}})
{ "_id" : ObjectId("567632624163f2ea4dd06e96"), "name" : "jack", "address" : [  "anhui",  "shanghai" ] }

where 【更灵活更强大】

可以灌输js代码，所以会有最大的灵活性。

db.person.find({"$where":function(){return this.name=="hxc19" && this.age==1}})
{ "_id" : ObjectId("56760f3c5001a3b4af601567"), "name" : "hxc19", "age" : 1 }
db.person.find({"$where":function(){ var i=1; return (this.age/1)==1 }})
{ "_id" : ObjectId("56760f3c5001a3b4af601567"), "name" : "hxc19", "age" : 1 }db.person.find({"$where":function(){return ( this.age>1&& this.age<2); }})
{ "_id" : ObjectId("56760f3c5001a3b4af601568"), "name" : "hxc20", "age" : 1.0526315789473684 }
{ "_id" : ObjectId("56760f3c5001a3b4af601569"), "name" : "hxc21", "age" : 1.105263157894737 }
{ "_id" : ObjectId("56760f3c5001a3b4af60156a"), "name" : "hxc22", "age" : 1.1578947368421053 }
{ "_id" : ObjectId("56760f3c5001a3b4af60156b"), "name" : "hxc23", "age" : 1.2105263157894737 }