mongodb-lectures/4.MONGO_ADVANCED_FIND.md

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
2. {name:1, _id: 0} excludes _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