$in

$in
The $in operator selects the documents where the valueof a field equals any value in the specified array. To specify an$in expression, use the following prototype:

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

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

If the field holds an array, then the $in operatorselects the documents whose field holds an array that containsat least one element that matches a value in the specified array(e.g. <value1>, <value2>, etc.)

Changed in version 2.6: MongoDB 2.6 removes the combinatorial limit for the $inoperator that exists for earlier versions of the operator.

Examples

Use the $in Operator to Match Values

Consider the following example:

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

This query selects all documents in the inventorycollection where the qty field value is either 5 or15. Although you can express this query using the$or operator, choose the $in operator ratherthan the $or operator when performing equality checks onthe same field.

Use the $in Operator to Match Values in an Array

The collection inventory contains documents that include the fieldtags, as in the following:

{ _id: 1, item: "abc", qty: 10, tags: [ "school", "clothing" ], sale: false }

Then, the following update() operation willset the sale field value to true where the tags field holdsan array with at least one element matching either "appliances" or"school".

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

For additional examples in querying arrays, see:

For additional examples in querying, see:

Query Documents

Use the $in Operator with a Regular Expression

The $in operator can specify matching values using regularexpressions of the form /pattern/. You cannot use $regexoperator expressions inside an $in.

Consider the following example:

db.inventory.find( { tags: { $in: [ /^be/, /^st/ ] } } )

This query selects all documents in the inventory collection wherethe tags field holds either a string that starts with be orst or an array with at least one element that starts with be orst.