How do I check if something exists in MongoDB?

In MongoDB, we can check the existence of the field in the specified collection using the $exists operator. When the value of $exists operator is set to true, then this operator matches the document that contains the specified field(including the documents where the value of that field is null).

Can MongoDB be indexed?

In addition, MongoDB can return sorted results by using the ordering in the index. Fundamentally, indexes in MongoDB are similar to indexes in other database systems. MongoDB defines indexes at the collection level and supports indexes on any field or sub-field of the documents in a MongoDB collection.

Which is not supported index type in MongoDB?

Neospatial is not a supported index type in MongoDB.

How do I query a nested field in MongoDB?

Query on Nested Field To specify a query condition on fields in an embedded/nested document, use dot notation ( “field. nestedField” ). When querying using dot notation, the field and nested field must be inside quotation marks.

Can MongoDB have multiple indexes?

Generally, MongoDB only uses one index to fulfill most queries. However, each clause of an $or query may use a different index, and in addition, MongoDB can use an intersection of multiple indexes.

How are indexes stored in MongoDB?

Index on a filed/fields is stored in order that we specify using B-Tree data structure. Stored in ordered Let see what does it mean’s and how it help’s. Index is created on the value of the filed referencing to the actual document stored.

Which type of index does MongoDB support?

Geospatial Index. To query geospatial data, MongoDB supports two types of indexes – 2d indexes and 2d sphere indexes.

What is secondary index in MongoDB?

MongoDB supports secondary indexes. To create an index, you just specify the field or combination of fields, and for each field specify the direction of the index for that field; 1 for ascending and -1 for descending. The following creates an ascending index on the i field: collection.

Which of the following are index is supported by MongoDB?

To query geospatial data, MongoDB supports two types of indexes – 2d indexes and 2d sphere indexes. 2d indexes use planar geometry when returning results and 2dsphere indexes use spherical geometry to return results.

Which is the method used to create index in MongoDB?

Creating an Index in MongoDB is done by using the “createIndex” method.

What is the query language for MongoDB?

MongoDB uses JavaScript as the main query language. If you install MongoDB you will be able to see the JavaScript language interpreter is installed by default. In terms of query language you can choose from a variety of scripting languages for MongoDB like python, PHP or perl.

What is collection in MongoDB?

The Collections. In MongoDB, a collection is a group of documents. A collection typically contains documents that have a similar topic (like Users, Products, Posts, etc). Collections are therefore, in many ways, similar to tables from the relational model.

What is Index in MongoDB?

In MongoDB, indexes plays a vital role in efficiently execution of the queries. Basically, if no index is defined in MongoDB, then it has to scan every document of a given collection. Hence, MongoDB uses index to reduce the number of documents to be scanned in a given collection.