$in
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$inThe
$inoperator selects the documents where the value of a field equals any value in the specified array. To specify an$inexpression, use the following prototype:For comparison of different BSON type values, see the specified BSON comparison order.
{ field: { $in: [<value1>, <value2>, ... <valueN> ] } } If the
fieldholds an array, then the$inoperator selects the documents whosefieldholds an array that contains at least one element that matches a value in the specified array (for example,<value1>,<value2>, and so on).The
$inoperator compares each parameter to each document in the collection, which can lead to performance issues. To improve performance:It is recommended that you limit the number of parameters passed to the
$inoperator to tens of values. Using hundreds of parameters or more can negatively impact query performance.Create an index on the
fieldyou want to query.
Note
This document describes the
$inquery operator. For the$inaggregation operator, see $in (aggregation).
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 } } )
For additional examples in querying arrays, see:
For additional examples in querying, see:
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 either a string that starts with be or
st or an array with at least one element that starts with be or
st.