$unwind stage do in a MongoDB aggregation pipeline?The $unwind stage takes an array field from each document and creates a separate document for each element in that array. This 'flattens' the array so you can work with each element individually.
$unwind affect documents that have an empty array or missing array field?By default, $unwind removes documents where the array is empty or the field is missing. You can change this behavior with the preserveNullAndEmptyArrays option to keep those documents.
{ name: 'Alice', hobbies: ['reading', 'swimming'] }, what will $unwind: '$hobbies' produce?It will produce two documents:<br>{ name: 'Alice', hobbies: 'reading' }<br>{ name: 'Alice', hobbies: 'swimming' }
$unwind to keep documents that have empty or missing arrays?You can use { preserveNullAndEmptyArrays: true } inside $unwind to keep documents even if the array is empty or missing.
$unwind useful when working with arrays in MongoDB?It helps to break down arrays into individual elements so you can filter, group, or sort based on each element separately, making data analysis easier.
$unwind stage do in MongoDB?$unwind splits each element of an array into its own document, effectively flattening the array.
$unwind on that field?By default, $unwind removes documents where the array is empty or missing.
$unwind to keep documents with empty or missing arrays?The correct option is preserveNullAndEmptyArrays: true.
{ name: 'Bob', tags: ['fun', 'smart'] }, what does $unwind: '$tags' produce?$unwind creates one document per array element.
$unwind in an aggregation pipeline?$unwind helps to flatten arrays so you can work with each element individually.
$unwind stage works in MongoDB and why it is useful.$unwind and how to change this behavior.