MongoDB Learning notes Aggregation Pipeline

Aggregation Pipeline:

Common operators introduce:

$project: Include, exclude, rename, and display fields

$match: query, need the same parameters as find ()

$limit: Limit the number of results

$skip: Ignore the number of results

$sort: Sort results by a given field

$group: Combining results by given expression

$lookup: Left Connection

$unwind: Expanding an embedded array

Define comments and LEFTT collections:

$project:

$match:

$limit:

$skip:

$sort:

$group:

$lookup:

$unwind:

MongoDB Learning notes Aggregation Pipeline