$in¶
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$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.
If the
field
holds an array, then the$in
operator selects the documents whosefield
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:
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:
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"
.
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:
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
.