Logical operators in mongoDB help us build logical combinations of multiple criteria in the same query.

Let’s have a look at the $and operator.

In a MongoDB Atlas cloud database, I have a products collection that contain the following four records:

 [
   {
     _id: new ObjectId("61a366483394265a2770d75c"),
     name: 'Airpods Pro',
     brand: 'Apple',
     category: 'Earphones',
     price: 99.99,
     soldQty: 240,
     __v: 0
   },
   {
     _id: new ObjectId("61a366483394265a2770d75d"),
     name: 'MacBook Pro',
     brand: 'Apple',
     category: 'Laptops',
     price: 1499.99,
     soldQty: 110,
     __v: 0
   },
   {
     _id: new ObjectId("61a366483394265a2770d75e"),
     name: 'Canon 80D DSLR Camera',
     brand: 'Cannon',
     category: 'Camera',
     price: 1099,
     soldQty: 360,
     __v: 0
   },
   {
     _id: new ObjectId("61a366483394265a2770d75f"),
     name: 'IE 300',
     brand: 'Sennheiser',
     category: 'Earphones',
     price: 299.99,
     soldQty: 540,
     __v: 0
   }
 ]

Using the $and operator we can have any number of conditions wrapped in an array and the operator will return only the documents that satisfy all the conditions.

Let’s say we want to determine the number of products that are from the brand Apple and belong to the category Earphones.

The query must have two conditions:

• The field brand should have a value of Apple.
• The field category should have a value of Earphones.

We can write the query using the $and operator, as shown below:

const query = async () => {
  const result = await Product.countDocuments({
    $and: [{ brand: "Apple" }, { category: "Earphones" }],
  })

  console.log(result)
}

query()

Executing the query above gives us the following result:

1

Note that in MongoDB queries, the $and operator is implicit and included by default if a query document has more than one condition.

For example, the following query can be rewritten without using the $and operator and gives the same result:

const query = async () => {
  const result = await Product.countDocuments({
    brand: "Apple",
    category: "Earphones",
  })

  console.log(result)
}

query()

So, we don’t have to use the $and operator explicitly, unless we want to make our code more readable.