logical-operators.md

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Logical query operators

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

Operator	Description
$and	Joins all query expressions with a logical AND operator
$or	Joins all query expressions with a logical OR operator
$not	Returns all documents that do NOT match a query expression
$nor	Returns all documents that do not match any of the query expressions

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'] }
    ]
  }
]