How do you match an array element in MongoDB?

How do you match an array element in MongoDB?

The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria. If you specify only a single condition in the $elemMatch expression, and are not using the $not or $ne operators inside of $elemMatch , $elemMatch can be omitted.

How do I index an array in MongoDB?

To index a field that holds an array value, MongoDB creates an index key for each element in the array. These multikey indexes support efficient queries against array fields. Multikey indexes can be constructed over arrays that hold both scalar values [1] (e.g. strings, numbers) and nested documents.

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 a composite key in MongoDB?

MongoDB and composite primary keys

1. Use an object for the primary key that is made up of 2 values (as suggested here)
2. Use a standard auto-generated mongo object id as the primary key, store my key in two separate fields, and then create a composite index on those two fields.
3. Make the primary key a hash of the 2 uuids.

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 run a query in MongoDB?

How to Execute Database Query in MongoDB

1. use DATABASE_NAME command is used to create database Example: >use hdfc switched to db mydb.
2. db command is used to check currently selected database Example: >db mydb.
3. show dbs command check all database lists Example: >show dbs local 0.78125GB test 0.23012GB.

How to query an array in mongo shell?

To query if the array field contains at least one element with the specified value, use the filter { : } where is the element value. The following example queries for all documents where tags is an array that contains the string “red” as one of its elements: Mongo Shell. Compass.

How to specify equality for an array in MongoDB?

To specify equality condition on an array, use the query document eq( , ) where is the exact array to match, including the order of the elements. To specify equality condition on an array, use the query document { : } where is the exact array to match, including the order of the elements.

How to remove an array from a MongoDB document?

If you want to remove array element from mongodb document’s array key then we can use $pull operator. This operator removes array elements based on matching condition. Lets take the previous example where we added some new elements to skills array key now are going to remove them.

How to do a reasonable query in MongoDB?

I’d suggest a schema change so that you can actually do reasonable queries in MongoDB. Then, you could index on “settings.value”, and do a query like: The change really is simple …, as it moves the setting name and setting value to fully indexable fields, and stores the list of settings as an array.