MongoDB distinct aggregation

Question

I m working on a query to find cities with most zips for each state   db zips distinct  state   db zips aggregate     group   id  state   state   city   city   numberOfzipcodes   sum 1       sort  numberOfzipcodes -1        The aggregate part of the query seems to work fine  but when I add the distinct I get an empty result   Is this because I have state in the id  Can I do something like distinct   id state

User · Answer

You can call  setUnion on a single array  which also filters dupes      project   Package  1  deps     setUnion     deps Package

User · Answer

You can use  addToSet with the aggregation framework to count distinct objects   For example   db collectionName aggregate         group    id  null  uniqueValues    addToSet    fieldName

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SQL Query   group by  amp  count of distinct   select city count distinct emailId   from TransactionDetails group by city    Equivalent mongo query would look like this   db TransactionDetails aggregate      group   id   CITY      cityName   uniqueCount    addToSet    emailId        project   CITY  1 uniqueCustomerCount   size   uniqueCount

User · Answer

Distinct and the aggregation framework are not inter-operable   Instead you just want   db zips aggregate          group   id  city   city   state   state    numberOfzipcodes   sum 1            sort  numberOfzipcodes -1          group   id    id state   city   first    id city                   numberOfzipcode   first   numberOfzipcodes

[mongodb] MongoDB distinct aggregation

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