$ne

Match Document Fields That Are Not Equal

Select all documents in the inventory collection where quantity is not equal to 20. This query also selects documents that do not have the quantity field:

db.inventory.find( { quantity: { $ne: 20 } } )

{
 _id: ObjectId("61ba667dfe687fce2f042420"),
 item: 'nuts',
 quantity: 30,
 carrier: { name: 'Shipit', fee: 3 }
},
{
 _id: ObjectId("61ba667dfe687fce2f042421"),
 item: 'bolts',
 quantity: 50,
 carrier: { name: 'Shipit', fee: 4 }
},
{
 _id: ObjectId("61ba667dfe687fce2f042422"),
 item: 'washers',
 quantity: 10,
 carrier: { name: 'Shipit', fee: 1 }
}

The SQL equivalent to this query is:

SELECT * FROM INVENTORY WHERE QUANTITIY != 20

Update Based on Not Equal Embedded Document Fields

The following example sets the price field based on a $ne comparison against a field in an embedded document. The updateMany() operation searches for an embedded document, carrier, with a subfield named fee. It uses $set to update the price field to 9.99 in each document where fee has a value that does not equal 1 or where the fee subfield does not exist:

db.inventory.updateMany(
   { "carrier.fee" : { $ne: 1 } },
   { $set: { "price": 9.99 } }
)

{
 _id: ObjectId("61ba66e2fe687fce2f042423"),
 item: 'nuts',
 quantity: 30,
 carrier: { name: 'Shipit', fee: 3 },
 price: 9.99
},
{
 _id: ObjectId("61ba66e2fe687fce2f042424"),
 item: 'bolts',
 quantity: 50,
 carrier: { name: 'Shipit', fee: 4 },
 price: 9.99
},
{
 _id: ObjectId("61ba66e2fe687fce2f042425"),
 item: 'washers',
 quantity: 10,
 carrier: { name: 'Shipit', fee: 1 }
}

The SQL equivalent to this query is:

UPDATE INVENTORY SET PRICE = '9.99' WHERE carrierfee != 1

The inequality operator $ne is not very selective since it often matches a large portion of the index. As a result, in many cases, a $ne query with an index may perform no better than a $ne query that must scan all documents in a collection. See also Query Selectivity.

Arrays

When comparing arrays, $ne matches documents where the document array differs from the array specified in $ne. Specifically, $ne matches any of these documents where the arrays:

• have different element values or strings

• have elements in a different order

• have a different number of elements

• are missing from a document

For example, the following query returns inventory documents where the type array differs from [ "hardware", "fasteners" ]:

db.inventory.find( { type: { $ne: [ "hardware", "fasteners" ] } } )

The following complete example adds a type array to two inventory documents and runs a query with $ne:

// Update the nuts document to include a type array
db.inventory.updateOne(
   { item: "nuts" },
   { $set: { type: [ "hardware" ] } }
)
// Update the bolts document to include a type array
db.inventory.updateOne(
   { item: "bolts" },
   { $set: { type: [ "hardware", "fasteners" ] } }
)
// Find documents where the type array differs from [ "hardware", "fasteners" ]
db.inventory.find( { type: { $ne: [ "hardware", "fasteners" ] } } )

Output shows the nuts document because the array differs from [ "hardware", "fasteners" ], and the washers document because it doesn't have a type array:

[
  {
    _id: ObjectId('679d26907c5a58595234305c'),
    item: 'nuts',
    quantity: 30,
    carrier: { name: 'Shipit', fee: 3 },
    type: [ 'hardware' ]
  },
  {
    _id: ObjectId('679d26907c5a58595234305e'),
    item: 'washers',
    quantity: 10,
    carrier: { name: 'Shipit', fee: 1 }
  }
]

The following query reverses the elements in the array:

db.inventory.find( { type: { $ne: [ "fasteners", "hardware" ] } } )

Because the type array in the bolts document is [ "hardware", "fasteners" ], which differs from [ "fasteners", "hardware" ], the query returns the bolts document in addition to the nuts and washers documents:

[
   {
      _id: ObjectId('679d26907c5a58595234305c'),
      item: 'nuts',
      quantity: 30,
      carrier: { name: 'Shipit', fee: 3 },
      type: [ 'hardware' ]
   },
   {
      _id: ObjectId('679d26907c5a58595234305d'),
      item: 'bolts',
      quantity: 50,
      carrier: { name: 'Shipit', fee: 4 },
      type: [ 'hardware', 'fasteners' ]
   },
   {
      _id: ObjectId('679d26907c5a58595234305e'),
      item: 'washers',
      quantity: 10,
      carrier: { name: 'Shipit', fee: 1 }
   }
]

$ne matches documents where the array doesn't contain the specified value and documents that don't have the array. For example:

db.inventory.find( { type: { $ne: "fasteners" } } )

The query returns the nuts document because the array [ "hardware" ] differs from "fasteners". Also, the query returns the washers document because the document doesn't have a type array. Query output:

[
   {
      _id: ObjectId('679d26907c5a58595234305c'),
      item: 'nuts',
      quantity: 30,
      carrier: { name: 'Shipit', fee: 3 },
      type: [ 'hardware' ]
   },
   {
      _id: ObjectId('679d26907c5a58595234305e'),
      item: 'washers',
      quantity: 10,
      carrier: { name: 'Shipit', fee: 1 }
   }
]