Mongodb增加、删除和查询操作

var x=db.c1.find();
x.hasNext();
x.next();
db.c1.find.count();
db.c1.find().toArray().length;
db.c4.insert({name:"user2",age:null});
db.c4.find({age:null});
db.c4.find(age:{$exists:1});
db.c4.find({age:{$exists:1,$in:[null]}});
db.c4.find({age:{$type:10}},name:"user1");
db.c4.find({age:{$exists:0}});
db.c3.find({name:"user1"},{post:$slice:1}});
db.c3.find({name:"user1"},{post:{$slice:[1,2]}});
db.c4.update({name:"user4"},{sex:"nan"});
db.c4.update({name:"user66"},{name:"user67"});
db.c4.update({name:"user66"},{name:"user67"},1);
db.c5.update({name:"user1"},{name:"user111"},0,1);
db.c5.update({name:"user1"},{$set:{name:"user111"}},0,1);
db.c5.update({},{$inc:score:10},0,1);
db.c5.update({},{$unset:{score:1}},0,1);
db.c5.update({name:"user1"},{$push:{arr:4}});
db.c5.remove();
db.c5.insert({name:"user1",arr:[1,3,2]});
db.c5.update({name:"user1"},{$addToSet:{arr:4}});
db.c5.update({name:"user1"},{$addToSet:{arr:{$each:[7,8,9]}}});
db.c5.update({name:"user1"},{$pop:{arr:1}});
db.c5.update({name:"user1"},{$pull:{arr:2}});
db.c5.update({name:"user1"},{$rename:{arr:"post"}});
db.c5.find();
db.c1.find({name:"user10"});