OPTIONS

$in

$in

The $in operator selects the documents where the value of 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 specified BSON comparison order.

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

If the field holds an array, then the $in operator selects the documents whose field holds an array that contains at 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 $in operator 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 inventory collection where the qty field value is either 5 or 15. Although you can express this query using the $or operator, choose the $in operator rather than the $or operator when performing equality checks on the same field.

Use the $in Operator to Match Values in an Array

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

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

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

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

Use the $in Operator with a Regular Expression

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

Consider the following example:

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

This query selects all documents in the inventory collection where the tags field holds an array that contains at least one element that starts with either be or st.

See also

find(), update(), $or, $set.

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