Logical query operators

Logical query operators return data based on specified query expressions that are either true or false.

For the examples in this section, insert the following documents into the catalog collection:

db.catalog.insertMany([
  {
    product: 'bottle',
    price: 15,
    stock: 1,
    discount: true,
    variation: [
      {
        size: ['small', 'medium', 'large']
      },
      {
        color: ['black', 'silver']
      }
    ]
  },
  {
    product: 'spoon',
    price: 500,
    stock: 0,
    discount: true,
    variation: [
      {
        size: ['small', 'medium', 'large']
      },
      {
        color: ['silver', 'white']
      }
    ]
  },
  {
    product: 'cup',
    price: 100,
    stock: 14,
    discount: true,
    variation: [
      {
        size: ['small', 'medium', 'large']
      },
      {
        color: ['red', 'black', 'white']
      }
    ]
  },
  {
    product: 'bowl',
    price: 56,
    stock: 5,
    discount: false,
    variation: [
      {
        size: ['small', 'medium', 'large']
      },
      {
        color: ['pink', 'white', 'red']
      }
    ]
  }
])

$and

Syntax: { $and: [ { <condition1> }, { <condition2> } , ... , { <condition3> } ] }

To satisfy more than one query condition when selecting documents, use the $and operator.

Example: Select documents that satisfy both of these expressions in the catalog collection:

• price field is less than 100 AND
• stock field is not 0

db.catalog.find({
  $and: [
    {
      price: {
        $lt: 100
      }
    },
    {
      stock: {
        $ne: 0
      }
    }
  ]
})

The output:

[
  {
    _id: ObjectId("639ba4a0071b6bed396a8f13"),
    product: 'bottle',
    price: 15,
    stock: 1,
    discount: true,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['black', 'silver'] }
    ]
  },
  {
    _id: ObjectId("639ba4a0071b6bed396a8f16"),
    product: 'bowl',
    price: 56,
    stock: 5,
    discount: false,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['pink', 'white', 'red'] }
    ]
  }
]

$or

Syntax: { $or: [ { <condition1> }, { <condition2> } , ... , { <conditionN> } ] }

To satisfy either one or more conditions in a query, use the $or operator to join the conditions.

Example: Select the documents that match these expressions:

• discount field is true and stock field is not 0 OR
• price field is less than or equal to 60

db.catalog.find({
  $or: [
    {
      $and: [
        {
          discount: true
        },
        {
          stock: {
            $ne: 0
          }
        }
      ]
    },
    {
      price: {
        $lte: 60
      }
    }
  ]
})

The output:

[
  {
    _id: ObjectId("639ba4a0071b6bed396a8f13"),
    product: 'bottle',
    price: 15,
    stock: 1,
    discount: true,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['black', 'silver'] }
    ]
  },
  {
    _id: ObjectId("639ba4a0071b6bed396a8f15"),
    product: 'cup',
    price: 100,
    stock: 14,
    discount: true,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['red', 'black', 'white'] }
    ]
  },
  {
    _id: ObjectId("639ba4a0071b6bed396a8f16"),
    product: 'bowl',
    price: 56,
    stock: 5,
    discount: false,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['pink', 'white', 'red'] }
    ]
  }
]

$not

Syntax: { <field>: { $not: { <condition> } } }

To select documents that fail to match a particular query condition, use the $not operator.

Example: The following operation selects documents that do not satisfy the specified expression, where the stock field is not less than 5.

db.catalog.find({
  stock: {
    $not: {
      $lt: 5
    }
  }
})

The output:

[
  {
    _id: ObjectId("639ba4a0071b6bed396a8f15"),
    product: 'cup',
    price: 100,
    stock: 14,
    discount: true,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['red', 'black', 'white'] }
    ]
  },
  {
    _id: ObjectId("639ba4a0071b6bed396a8f16"),
    product: 'bowl',
    price: 56,
    stock: 5,
    discount: false,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['pink', 'white', 'red'] }
    ]
  }
]

$nor

Syntax: { $nor: [ { <condition1> }, { <condition2> }, ... { <conditionN> } ] }

To select documents that fail to match any of the conditions in a specified query, use the $nor operator.

Example: Select the documents that fail to match any of these conditions:

• discount field is true and stock field is not 0
• price field is less than or equal to 60

db.catalog.find({
  $nor: [
    {
      $and: [
        {
          discount: true
        },
        {
          stock: {
            $ne: 0
          }
        }
      ]
    },
    {
      price: {
        $lte: 60
      }
    }
  ]
})

The output:

[
  {
    _id: ObjectId("639ba4a0071b6bed396a8f14"),
    product: 'spoon',
    price: 500,
    stock: 0,
    discount: true,
    variation: [
      { size: ['small', 'medium', 'large'] },
      { color: ['silver', 'white'] }
    ]
  }
]