how to use aggregations in mongodb - Wikitechy https://www.wikitechy.com/interview-questions/tag/how-to-use-aggregations-in-mongodb/ Interview Questions Mon, 04 Apr 2022 11:48:41 +0000 en-US hourly 1 https://wordpress.org/?v=6.9.4 https://www.wikitechy.com/interview-questions/wp-content/uploads/2025/10/cropped-wikitechy-icon-32x32.png how to use aggregations in mongodb - Wikitechy https://www.wikitechy.com/interview-questions/tag/how-to-use-aggregations-in-mongodb/ 32 32 What are Geospatial Indexes in MongoDB ? https://www.wikitechy.com/interview-questions/mongodb/what-are-geospatial-indexes-in-mongodb/ https://www.wikitechy.com/interview-questions/mongodb/what-are-geospatial-indexes-in-mongodb/#respond Mon, 04 Apr 2022 11:48:41 +0000 https://www.wikitechy.com/interview-questions/?p=4089
  • It allows you to efficiently execute spatial queries on a collection that contains geospatial shapes and points.
  • It was created by two fields, specify the location field first, then the second field.
  • In MongoDB, it has two types 2dsphere and 2d.
  • Indexes work with spherical geometries that model the surface of the earth based on the WGS84 datum is 2dsphere.
  • In this model, the surface of the earth is an oblate spheroid, meaning that there is some flattening at the poles.
  • Indexes for points stored on a two-dimensional plane is 2d.
  • In GeoJSON format 2dsphere allows you to specify geometries for points, lines, and polygons.
  • A point is given by a two-element array, representing [longitude, latitude].

    • For example,

                                       {
                                              "name" : "New York City",
                                              "loc" : {
                                                     "type" : "Point",
                                                     "coordinates" : [50, 2]
                                            }
                                      }

    A line is given by an array of points:

    For example,

    {
                                "name" : "Hudson River",
                                "loc" : {
                                      "type" : "LineString",
                                      "coordinates" : [[0,1], [0,2], [1,2]]
                               }
                          }
    ]]>     https://www.wikitechy.com/interview-questions/mongodb/what-are-geospatial-indexes-in-mongodb/feed/ 0     What are the aggregate functions of MongoDB ? https://www.wikitechy.com/interview-questions/mongodb/what-are-the-aggregate-functions-of-mongodb/ https://www.wikitechy.com/interview-questions/mongodb/what-are-the-aggregate-functions-of-mongodb/#respond Mon, 04 Apr 2022 11:28:07 +0000 https://www.wikitechy.com/interview-questions/?p=4085
  • The aggregation pipeline consists of stages, and each stage transforms the document in MongoDB.
  • In each state, the documents are taken as input and produce the resultant set of documents are now in the next stage (id available) the resultant documents taken as input and produce output, this process is going on till the last stage.
  • In other word, the aggregation pipeline is a multi-stage pipeline.
  • The basic pipeline stages provide filters that will perform like queries and the document transformation modifies the resultant document, and the other pipeline provides tools for grouping and sorting documents.
  • In aggregation, there are various functions used:

    • Sum :

    • This aggregation function is used to sum numeric values for the document in each group.

    Count :

    • This aggregation function is used to count total number of documents.

    Average :

    • This aggregation function is used to calculates the average of all given values from all documents.

    Minimum :

    • This aggregation function is used to get the minimum value from all the documents.

    Maximum :

    • This aggregation function is used to get the maximum value from all the documents.

    First :

    • This aggregation function is used to get the first document from the grouping.

    Last :

    • This aggregation function is used to get the last document from the grouping.
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