Updating Documents

Changing existing data uses updateOne() or updateMany(), paired with update operators that describe exactly what should change.

An isometric illustration of a pencil editing a highlighted field inside a document icon, with a small refresh arrow

$set — Change a Field's Value

db.users.updateOne(
  { name: "Karan Mehta" },
  { $set: { age: 23 } }
)

$inc — Increase or Decrease a Number

$inc adds (or, with a negative number, subtracts) a value to a numeric field — useful for counters, without needing to read the current value first:

db.products.updateOne(
  { name: "Notebook" },
  { $inc: { stock: -1 } }
)

$push — Add to an Array

db.users.updateOne(
  { name: "Karan Mehta" },
  { $push: { skills: "TypeScript" } }
)

$unset — Remove a Field

db.users.updateOne(
  { name: "Karan Mehta" },
  { $unset: { temporaryFlag: "" } }
)

updateMany() — Every Matching Document

db.users.updateMany(
  { isActive: false },
  { $set: { status: "archived" } }
)

A missing operator replaces the whole document

Forgetting the update operator and writing { age: 23 } instead of { $set: { age: 23 } } replaces the entire document with just { age: 23 }, deleting every other field. Always wrap changes in an operator like $set.