Search in a specified array in MongoDB
$inOperator searches within an array that you provide. For example, if you are given an array and want to search for one or more matching elements in a MongoDB collection, you can use $in.
Use $inthe operator to search for a specified array in MongoDB
$inThe operator finds documents where a field value is equal to any of the values in the provided array. Use the following prototype to specify $inan expression.
{ field: { $in: [<value1>, <value2>, ... <valueN> ] } }
For example, suppose you have the following collection.
{
_id:1,
name: "John",
age: 30
},
{
_id:2,
name: "Alex",
age: 23
},
{
_id:3,
name: "Murphy",
age: 25
},
{
_id:4,
name: "Alice",
age: 28
},
Now, you want to view _id = 2,3,4the documentation for . Therefore, the command will be as follows.
db.collection.find( {_id: { $in: [2, 3, 4] } } );
Alternatively, you can also send an array as a parameter. It can be useful when you are developing an application or a website.
let list=[2, 3, 4]
db.collection.find( { _id:{ $in: list} } )
promisesThis approach is useful when
working with JavaScript .
To avoid errors, you should pay attention to the ObjectId.Default _idprovided by MongoDB, _idwhich is of type ObjectId.
Therefore, when passing an array into $inthe argument of , it is best to convert each integer idto ObjectId, as shown below.
{ "_id" : { $in : [ObjectId('2'),ObjectId('3'),ObjectId('4')] } }
This method is more accurate because you provide _idthe exact data type of the through the parameter. It can $inalso be used for updateMany,,,, operations.updateOnedeleteOnedeleteMany
To learn $inmore about the operator, visit the official page here .
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