MongoDB Aggregation Operations

1, first example analysis of the following MongoDB aggregation operations:

• This operation indicates that the count quantity under each group is counted according to the whoisserver_id field grouping:

Db.anhui.aggregate ({$group: {_id:'$whoisserver _id', total:{$sum:1}})

The results of the query are as follows:

• If the total number of queries:

Db.anhui.aggregate ({$group: {_id:null, total:{$sum: 1}})

• The following query filters and then counts based on criteria

db.anhui.aggregate {$match: {mx:{$exists: 1}}},{$group: {_id: ' $whoisserver _id ', total:{  $sum: 1}})

• First filter the data equivalent to the where operation in the SQL statement, then group Count, and then match the information with a quantity greater than 30

db.anhui.aggregate {$match: {mx:{$exists: 1}}},{$group: {_id: ' $whoisserver _id ', total:{  $sum: 1}}},{$match: {total:{$gte: 30}})

The following is the data to be queried

Inquire

db.anhui.aggregate {$match: {mx:{$exists: 1}}},{$group: {_id: ' $mx. brand_id ', total:{  $sum: 1}})

MongoDB Aggregation Operations