MongoDB SELECT COUNT GROUP BY

Question

I am playing around with MongoDB trying to figure out how to do a simple  SELECT province  COUNT    FROM contest GROUP BY province   But I can t seem to figure it out using the aggregate function  I can do it using some really weird group syntax  db user group        key              province   true             initial              count   0             reduce   function obj  prev            if  true    null  if  true instanceof Array  prev count    true length          else prev count                But is there an easier faster way using the aggregate function

User · Answer

Mongo shell command that worked for me    db getCollection  lt collection name gt   aggregate     match      lt key gt      lt value to match gt         group      id      lt group by attribute gt      group by attribute

User · Answer

If you need multiple columns to group by  follow this model  Here I am conducting a count by status and type     db BusinessProcess aggregate         group              id                status    status               type    type                     count                 sum  1

User · Answer

I need some extra operation based on the result of aggregate function  Finally I ve found some solution for aggregate function and the operation based on the result in MongoDB  I ve a collection Request with field request  source  status  requestDate   Single Field Group By  amp  Count   db Request aggregate          group      id   source   count   sum 1         Multiple Fields Group By  amp  Count   db Request aggregate          group      id  source   source  status   status    count   sum 1         Multiple Fields Group By  amp  Count with Sort using Field   db Request aggregate          group      id  source   source  status   status    count   sum 1           sort    id source  1        Multiple Fields Group By  amp  Count with Sort using Count   db Request aggregate          group      id  source   source  status   status    count   sum 1           sort   count  -1

User · Answer

This would be the easier way to do it using aggregate   db contest aggregate          group      id   province   count   sum 1

User · Answer

This type of query worked for me    db events aggregate   group    id     date   number      sum   1         See http   docs mongodb org manual tutorial aggregation-with-user-preference-data

User · Answer

Starting in MongoDB 3 4  you can use the  sortByCount aggregation      Groups incoming documents based on the value of a specified expression  then computes the count of documents in each distinct group    https   docs mongodb com manual reference operator aggregation sortByCount   For example   db contest aggregate          sortByCount    province

User · Answer

Additionally if you need to restrict the grouping you can use   db events aggregate         match   province   ON           group    id    date   number    sum  1

[mongodb] MongoDB SELECT COUNT GROUP BY

Examples related to mongodb

Examples related to group-by

Examples related to aggregation-framework