$nin¶

$nin¶

Syntax: { field: { $nin: [ <value1>, <value2> ... <valueN> ]} }

$nin selects the documents where:

the field value is not in the specified array or
the field does not exist.

For comparison of different BSON type values, see the specified BSON comparison order.

Consider the following query:

db.inventory.find( { qty: { $nin: [ 5, 15 ] } } )

This query will select all documents in the inventory collection where the qty field value does not equal 5 nor 15. The selected documents will include those documents that do not contain the qty field.

If the field holds an array, then the $nin operator selects the documents whose field holds an array with no element equal to a value in the specified array (e.g. <value1>, <value2>, etc.).

Consider the following query:

db.inventory.update( { tags: { $nin: [ "appliances", "school" ] } }, { $set: { sale: false } } )

This update() operation will set the sale field value in the inventory collection where the tags field holds an array with no elements matching an element in the array ["appliances", "school"] or where a document does not contain the tags field.

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