group() - Group values JSON command
Groups values for the collection in a query. More command options are available by using the aggregate() command with the $group task.
Syntax diagram
Command parameters
- definition
- This parameter specifies the fields that must be grouped.
- query
- This parameter specifies a filter for selecting a subset of documents.
- limit
- This parameter specifies an integer value that indicates the maximum size of the result set.
- offset
- This parameter finds the document that the query requested after it skips a specified number of rows.
Example
Calculate the average price of books per author:
db.books.group({"_id": {"author": 1}, "sumqty": {"$sum": "$qty"}})Row 1:
{
"_id":"Doe",
"sumqty":17481
}
Row 2:
{
"_id":"Smith",
"sumqty":5926
}