二、Mongodb实战之——Mongodb Shell实现简单插入和查询

insert

向集合中插入文档

source code

function (obj, _allow_dot) {
    if (!obj) {
        throw "no object passed to insert!";
    }
    if (!_allow_dot) {
        this._validateForStorage(obj);
    }
    if (typeof obj._id == "undefined" && !Array.isArray(obj)) {
        var tmp = obj;
        obj = {_id:new ObjectId};
        for (var key in tmp) {
            obj[key] = tmp[key];
        }
    }
    this._db._initExtraInfo();
    this._mongo.insert(this._fullName, obj);
    this._lastID = obj._id;
    this._db._getExtraInfo("Inserted");
}

example：

>db.users.insert({"userName":"chjzh","pwd":"123"})

find

在集合中查询符合条件的文档,find()返回集合中所有文档

source code

function (query, fields, limit, skip, batchSize, options) {
    return new DBQuery(this._mongo, this._db, this, this._fullName, this._massageObject(query), fields, limit, skip, batchSize, options || this.getQueryOptions());
}

example

>db.users.find({"userName":"chjzh"})

save

向集合中插入文档，与insert不同的是，若集合中存在重复的id则insert不做插入，而save则更改原来的内容为新内容

source code

function (obj) {
    if (obj == null || typeof obj == "undefined") {
        throw "can't save a null";
    }
    if (typeof obj == "number" || typeof obj == "string") {
        throw "can't save a number or string";
    }
    if (typeof obj._id == "undefined") {
        obj._id = new ObjectId;
        return this.insert(obj);
    } else {
        return this.update({_id:obj._id}, obj, true);
    }
}

example

>db.users.save({"userName":"chjzh","pwd":"111111"})

count

统计集合中满足条件的文档个数

source code

function (x) {
    return this.find(x).count();
}

example

>db.users.count()