MongoDB Find

Reading Documents with find()

Every read operation in MongoDB starts with db.collection.find(). Called with no arguments, it returns a cursor over every document in the collection. Called with a query filter as its first argument, it returns only the documents that match. Unlike a relational SELECT, there is no separate query language to learn — filters are just JSON documents describing the shape of the data you want back.

db.products.find()

// Equivalent, explicit empty filter
db.products.find({})

Filtering with Field Equality

The simplest filter matches a field against an exact value. { field: value } tells MongoDB to return only documents where that field equals value. You can combine several fields in the same filter object; by default MongoDB treats multiple fields as an implicit AND, so every condition must be true for a document to match.

// Single-field equality
db.products.find({ category: 'electronics' })

// Multiple fields (implicit AND)
db.products.find({
  category: 'electronics',
  inStock: true
})

findOne() vs find()

find() always returns a cursor, even when only one document matches — you have to iterate it (or call .toArray() in the shell) to see the data. findOne() skips the cursor entirely and hands back a single document object directly, or null if nothing matched. Reach for findOne() whenever your application logic only ever needs the first match, such as looking up a user by a unique email address.

// Returns the first matching document, or null
const user = db.users.findOne({ email: 'ada@example.com' })

// Returns a cursor you must iterate
db.users.find({ email: 'ada@example.com' }).forEach(doc => {
  print(doc.name)
})

Projections: Choosing Which Fields Come Back

Both find() and findOne() accept a second argument called a projection. It's a document that lists which fields to include (1) or exclude (0). The _id field is included automatically unless you explicitly set _id: 0. Projections reduce network traffic and keep your application code from accidentally depending on fields it doesn't need.

• { field: 1 } — include only this field (plus _id)
• { field: 0 } — include everything except this field
• You cannot mix 1s and 0s in the same projection, except alongside _id: 0
• Projections do not filter documents — they only shape which fields appear

// Only return name and price (plus _id)
db.products.find(
  { category: 'electronics' },
  { name: 1, price: 1 }
)

// Return everything except the internal notes field
db.products.find(
  { category: 'electronics' },
  { internalNotes: 0 }
)