MongoDB

// Insert
db.users.insertOne({ name: "Alice", age: 30, tags: ["admin"] });
db.users.insertMany([{ name: "Bob" }, { name: "Carol" }]);

// Find
db.users.find({ age: { $gt: 25 } });
db.users.find({ name: /^A/i });      // Regex
db.users.findOne({ _id: ObjectId("...") });
db.users.find({}).sort({ age: -1 }).limit(10).skip(20);

// Projection (select fields)
db.users.find({}, { name: 1, email: 1, _id: 0 });

// Update
db.users.updateOne(
  { _id: id },
  { $set: { age: 31 }, $push: { tags: "editor" } }
);
db.users.updateMany({ age: { $lt: 18 } }, { $set: { minor: true } });

// Upsert
db.users.updateOne({ email: "[email protected]" }, { $set: { name: "Alice" } }, { upsert: true });

// Delete
db.users.deleteOne({ _id: id });
db.users.deleteMany({ status: "inactive" });

db.orders.aggregate([
  // Stage 1: Filter
  { $match: { status: "completed", createdAt: { $gte: ISODate("2024-01-01") } } },

  // Stage 2: Join with users
  { $lookup: {
    from: "users",
    localField: "userId",
    foreignField: "_id",
    as: "user"
  }},
  { $unwind: "$user" },

  // Stage 3: Group & aggregate
  { $group: {
    _id: "$user.country",
    totalRevenue: { $sum: "$amount" },
    orderCount: { $sum: 1 },
    avgOrder: { $avg: "$amount" }
  }},

  // Stage 4: Sort & limit
  { $sort: { totalRevenue: -1 } },
  { $limit: 10 },

  // Stage 5: Reshape output
  { $project: {
    country: "$_id",
    totalRevenue: 1,
    orderCount: 1,
    _id: 0
  }}
]);