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How do I query an array in MongoDB?

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How do I query an array in MongoDB?

To query if the array field contains at least one element with the specified value, use the filter { : } where is the element value. To specify conditions on the elements in the array field, use query operators in the query filter document: { : { : , } }

How do I filter an array field in MongoDB?

Filter MongoDB Array Element Using $Filter Operator

  1. input – This represents the array that we want to extract.
  2. cond – This represents the set of conditions that must be met.
  3. as – This optional field contains a name for the variable that represent each element of the input array.

What is elemMatch?

Definition. $elemMatch. The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria.

What is an array in MongoDB?

MongoDB Array is a flexible document structure; it will make it possible to have a field with array as a value in MongoDB. We can define an array of string, integer, embedded documents, Jason and BSON data types, array in it can be defined as any form of data types.

How do I create an array in MongoDB?

Case 1 − Create array with MongoDB. If you want to create an array of field UserName and do not want the field _id, use the below query. If you want to create an array with field name _id only, use the below query.

How do I push data into an array in MongoDB?

If the field is absent in the document to update, $push adds the array field with the value as its element. If the field is not an array, the operation will fail. If the value is an array, $push appends the whole array as a single element. To add each element of the value separately, use the $each modifier with $push .

How do I filter a field in MongoDB?

Set Query Filter

  1. In the Filter field, enter a filter document. You can use all of the MongoDB query operators except the $text and $expr operators. Example. The following filter only returns documents which have a Country value of Brazil :
  2. Click Find to run the query and view the updated results. click to enlarge.

How do I match an array object in MongoDB?

To search the array of object in MongoDB, you can use $elemMatch operator. This operator allows us to search for more than one component from an array object.

How do I test multiple values in MongoDB?

MongoDB provides the find() that is used to find multiple values or documents from the collection. The find() method returns a cursor of the result set and prints all the documents. To find the multiple values, we can use the aggregation operations that are provided by MongoDB itself.

How do I add values to an array in MongoDB?

If the value is an array, $push appends the whole array as a single element. To add each element of the value separately, use the $each modifier with $push . For an example, see Append Multiple Values to an Array.

How do you update an element in an array in MongoDB?

You can use the updateOne() or updateMany() methods to add, update, or remove array elements based on the specified criteria. It is recommended to use the updateMany() method to update multiple arrays in a collection.

What is $$ root MongoDB?

$replaceRoot. New in version 3.4. Replaces the input document with the specified document. The operation replaces all existing fields in the input document, including the _id field. You can promote an existing embedded document to the top level, or create a new document for promotion (see example).

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