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SOLVED: MongoDB - Query - Top Document per Group

mils:

I have got the next SQL (mysql) question, as well as I might similar to transform it to MongoDB. It's mainly getting the highest 1 doc inwards each grouping:


SELECT A.* 
FROM adverts AS A
INNER JOIN (SELECT id 
            FROM adverts
            WHERE userId = 1
            GROUP BY ad_code
            HAVING MAX(ad_timestamp)) AS B ON B.id = A.id

From what I have got learn to date at that place are a number of methods to combination information inwards MongoDB (more than information at MongoDB aggregation comparison: group(), $group and MapReduce):

  • grouping (does non piece of work on sharded collections)
  • MapReduce
  • $grouping

I'm attempting to unravel this with the MongoDB aggregation framework. To date I have got this:


db.adverts.combination([
    ,
    
])

However this does non homecoming the _ids of the matching paperwork, simply the advertisement code as well as max timestamp, so I can't exercise the information to acquire entire paperwork.

This inquiry seems really related, however it doesn't appear to unravel the identical number I'm having: Query one document per association from MongoDB

Thanks



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