MongoDB v5.0.5 query using hour only-CodePudding

First occasion experimenting with dates and times in MongoDB.

Currently, I have correctly inserted UTC dates into my documents:

{
 "Value": 10
 "DateTime": {
        "$date": "2013-08-23T08:00:00.000Z"
    },
}

I want to query the data to return all of the 'value' and datetime fields for all documents in which the hour is 08. I have gotten as far as:

db.readings.aggregate([{$project:{hour:{$hour:"$DateTime"}}},{$match:{hour:{"$in":[08]}}}])

Which returns the _id and "hour": 8 for all matching entries but I'm confused at how to proceed. It seems an unnecessarily complicated way to search and so I wonder if I am barking up the wrong tree here? Admittedly, I am somewhat out of my depth so some guidance would be appreciated.

CodePudding user response：

You can try $expr expression operator to use aggregation operators ($hour) in query,

$expr to use aggregation operators
$hour will return an hour from the date
$eq to match hour and input hour 8

db.collection.find({
  $expr: {
    $eq: [
      { $hour: "$DateTime" },
      8
    ]
  }
})

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