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Mongo - Advanced Find

Lesson Objectives#

  1. Explain Field Selection
  2. Explain Ordering
  3. Explain Paging
  4. Explain Count

Explain Field Selection#

  1. db.employees.find({}, {name: 1});
  • 1 for include
  • 0 for exclude
  1. {name:1, _id: 0} excludes the id

Explain Ordering#

  1. db.employees.find().sort({name: 1, salary: -1})
  • 1 for ascending
  • -1 for descending
  • won't sort on large set without index

Explain Paging#

  1. db.employees.find().sort({weight: -1}).limit(2).skip(1)
  • can help avoid issues when sorting on large un-indexed fields

Explain Count#

  1. db.employees.find({salary: {$gt: 50}}).count()
  • usual count is just a shortcut to this