Operators for updates & arrays in MongoDB

medium · MongoDB — Documents & data modeling

$push → adds a value to an array Example: db.users.updateOne({ name: "Rahul" }, { $push: { hobbies: "cricket" } }) $push with $each → adds multiple values db.users.updateOne({ name: "Rahul" }, { $push: { hobbies: { $each: ["music", "reading"] } } }) $addToSet → adds only if value is not already present (no duplicates) db.users.updateOne({ name: "Rahul" }, { $addToSet: { hobbies: "cricket" } }) $pull → removes a specific value from array db.users.updateOne({ name: "Rahul" }, { $pull: { hobbies: "cricket" } }) $pop → removes first or last element 1 → last element, -1 → first element db.users.updateOne({ name: "Rahul" }, { $pop: { hobbies: 1 } }) $set (for arrays) → updates value at specific index db.users.updateOne({ name: "Rahul" }, { $set: { "hobbies.0": "football" } }) $ (positional operator) → updates matched element db.users.updateOne({ hobbies: "cricket" }, { $set: { "hobbies.

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quot;: "football" } }) $[] → updates all elements in array db.users.updateOne({}, { $set: { "scores.$[]": 100 } }) $[identifier] → updates elements based on condition db.users.updateOne({}, { $set: { "scores.$[e]": 100 } }, { arrayFilters: [{ "e": { $lt: 50 } }] }) Simple understanding: $push → add $addToSet → add without duplicates $pull → remove $pop → remove first/last $set → update $ / $[] / $[ ] → target specific elements

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