Create

Inserting Documents

  • insertOne(document)

    • Inserts a single document into a collection.
    • Example: 
        db.collectionName.insertOne({
  name: "John Doe",
  age: 30,
  city: "New York"
});

  • insertMany(documents)

    • Inserts multiple documents into a collection.
    • Example: 
        db.collectionName.insertMany([
  { name: "Alice", age: 25, city: "Los Angeles" },
  { name: "Bob", age: 28, city: "Chicago" }
]);

Read

Querying Documents

  • find(query)

    • Retrieves multiple documents that match the query.
    • Example: 
        db.collectionName.find({ age: { $gt: 25 } });

  • findOne(query)

    • Retrieves a single document that matches the query.
    • Example: 
        db.collectionName.findOne({ name: "John Doe" });

Query Operators

  • $eq (Equal)

    • Matches values that are equal to a specified value.
    • Example: 
        db.collectionName.find({ age: { $eq: 30 } });

  • $gt (Greater Than)

    • Matches values that are greater than a specified value.
    • Example: 
        db.collectionName.find({ age: { $gt: 25 } });

  • $lt (Less Than)

    • Matches values that are less than a specified value.
    • Example: 
        db.collectionName.find({ age: { $lt: 30 } });

Projection (Selecting Specific Fields)

  • Projection allows you to specify which fields to include or exclude in the results.
  • Example: 
      db.collectionName.find(
  { age: { $gt: 25 } },
  { projection: { name: 1, city: 1 } }
);
  • The above command retrieves only the name and city fields.

Update

Updating Documents

  • updateOne(filter, update)

    • Updates a single document that matches the filter.
    • Example:
      db.collectionName.updateOne(
  { name: "John Doe" },
  { $set: { age: 31 } }
);

  • updateMany(filter, update)

    • Updates multiple documents that match the filter.
    • Example:
      db.collectionName.updateMany(
  { city: "New York" },
  { $set: { status: "active" } }
);

Update Operators

  • $set

    • Sets the value of a field in a document.
    • Example:
      Copy code
db.collectionName.updateOne(
  { name: "John Doe" },
  { $set: { age: 31 } }
);

  • $unset

    • Removes a field from a document.
    • Example:
      db.collectionName.updateOne(
  { name: "John Doe" },
  { $unset: { city: "" } }
);

  • $inc

    • Increments the value of a field by a specified amount.
    • Example:
      db.collectionName.updateOne(
  { name: "John Doe" },
  { $inc: { age: 1 } }
);

Delete

Deleting Documents

  • deleteOne(filter)

    • Deletes a single document that matches the filter.
    • Example:
      db.collectionName.deleteOne({ name: "John Doe" });

  • deleteMany(filter)

    • Deletes multiple documents that match the filter.
    • Example:
      db.collectionName.deleteMany({ age: { $lt: 20 } });