Home / Questions / 47001
Accepted
Mario López Batres
Asked: 2020-02-01 09:52:39 +0800 CST 2020-02-01 09:52:39 +0800 CST

Query MongoDB

  • 772

I am trying to make a query in MongoDB, and it is not clear to me how to do it.

Through the following line, I get the displayed: enter image description here

I would like to know if there is any way to get only the field in question, ie "qfmSLTmr3tyZwykaA" and not everything that precedes it.

Or treat it somehow throughjavascript

javascript

2 Answers

  1. Best Answer

    When you perform a search in a collection and you want to exclude one or several fields, you can use 0 to indicate not to show the field:

    db.colleccion.find({}, {"nombre campo no requerido": 0 })

    to include it we use 1

    db.colleccion.find({}, {"nombre campo no requerido": 1 })

    In the case of what you are doing, you are obtaining all the elements of the collection but you only show the "building" field, while you exclude the "_id" field:

    db.terminales.find({}, {"edificio":1, "_id":0});

    with this result:

    "edificio": "qfmSLTmr3tyZwykaA"

    If you want to obtain only the value (or the values ​​of a certain field) it is obtained in this way:

    db.terminales.find().forEach(function(row) {print(row.edificio);})

    with this you will get only the value of the fieldedificio

    qfmSLTmr3tyZwykaA
    • 1

  2. If possible. This query method is called Projection . The method findaccepts two objects as parameters:

    1. Evaluation fields
    2. projection

    Your query will look like this when using Projection :

    db.terminales.find({}, { eficio: 1 } );

    The integer is binary, that is, it accepts only 0and 1. By default, the _idwill also be selected, if you don't want this behavior you can override it by setting 0the _id:

    db.terminales.find({}, { eficio: 1, _id: 0 } );
    • 0