MONGO DB QUERIES

mongo-commands.js

// Count an array that is embedded into document.

// Document:
{name: 'Pepito', tags: ['A', 'B', 'C', 'D']}

//Mongodb query:
db.employees.aggregate(
  {$match: {name : "Pepito"}}, 
  {$unwind: "$tags"},
  {$group: {_id: null, number: {$sum: 1 }}}
)

// OR
db.employees.aggregate(
  [
    {
      $project: 
      {
        count_tags: {$size: 'tags'}
      }
    }
  ]
)

// How to import a dump?
// 1. Using default location for db '/data/db'
//    Go to file where  'dump' directory is available and execute following command:

      $ mongorestore

// 2. Using custom location for db (using '/path/to/pets' instead of 'using /data/db'

      $ mongorestore -d pets /path/to/pets