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• $in

$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.

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{ 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:

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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:

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{ _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".

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

For additional examples in querying arrays, see:

• Query an Array
• Query an Array of Embedded Documents

For additional examples in querying, see:

• Query Documents

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:

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

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

See also

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

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