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- db.collection.count()
db.collection.count()¶
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Definition¶
-
db.collection.
count
(<query>)¶ Returns the count of documents that would match a
find()
query. Thedb.collection.count()
method does not perform thefind()
operation but instead counts and returns the number of results that match a query.The
db.collection.count()
method has the following parameter:Parameter Type Description query
document The query selection criteria.
See also
Behavior¶
On a sharded cluster, db.collection.count()
can result in an inaccurate count if
orphaned documents exist or if a
chunk migration is in progress.
To avoid these situations, on a sharded cluster, use the
$group
stage of the db.collection.aggregate()
method to $sum
the documents. For example, the following
operation counts the documents in a collection:
To get a count of documents that match a query condition, include the
$match
stage as well:
See Perform a Count for an example.
Examples¶
Count all Documents in a Collection¶
To count the number of all documents in the orders
collection, use
the following operation:
This operation is equivalent to the following:
Count all Documents that Match a Query¶
Count the number of the documents in the orders
collection with the field ord_dt
greater than new
Date('01/01/2012')
:
The query is equivalent to the following: