MongoDb查询

//数据转换类型mongodb过滤数据并聚合

db.IotMeterGasUsedRecord_2020.aggregate([{
   // 获取字段 
　　$project: {
        _id: 0,
　　　　 // 类型转换
        RecordUsedValue: {
            $toDouble: {
                $substrBytes: ["$RecordUsedValue", 0, 4]
            }
        },
        RecordUserId: 1
    }
}, {
    $group: {
        _id: "$RecordUserId",
        RecordUsedValue: {
            $sum: ("$RecordUsedValue")
        }
    }
}]);

//过滤重复数据

db.IotMeterUnReportRecord_2021.aggregate([
    {
        $group:{_id:{RecordUserId:'$RecordUserId',RecordYear:'$RecordYear',RecordMonth:'$RecordMonth',RecordDay:'$RecordDay'},count:{$sum:1},dups:{$addToSet:'$_id'}}
    },
    {
        $match:{count:{$gt:1}}
    }

    ])    
    .forEach(function(it){
　　　　　　// 所动首条
         it.dups.shift();
            db.IotMeterUnReportRecord_2021.remove({_id: {$in: it.dups}});

    });
db.IotMeterUnReportRecord_2020.aggregate([
    {
        $group:{_id:{RecordUserId:'$RecordUserId',RecordYear:'$RecordYear',RecordMonth:'$RecordMonth',RecordDay:'$RecordDay'},count:{$sum:1},dups:{$addToSet:'$_id'}}
    },
    {
        $match:{count:{$gt:1}}
    }

    ]).forEach(function(it){

         it.dups.shift();
            db.IotMeterUnReportRecord_2020.remove({_id: {$in: it.dups}});

    });

取分组条数

db.getCollection('IotMeterUnReportRecord_2021').aggregate([{
    $group: {
        _id: "$RecordUserId",
        id: {
            $first: "$_id"
        }
    }
}, {
    $project: {
        _id: 0,
        id: "$id"
    }
}, {
    $sort: {
        RecordAddDate: - 1
    }
}, {
    $skip: 10
}, {
    $limit: 10
}])


db.getCollection('IotMeterUnReportRecord_2021').aggregate([{
    $group: {
        _id: "$RecordUserId",
        id: {
            $first: "$_id"
        },
        count: {
            $sum: 1
        }
    }
}, {
    $project: {
        _id: 0,
        id: "$id"
    }
}, {
    $sort: {
        RecordAddDate: - 1
    }
}, {
    $group: {
        _id: "$id",
        count: {
            $sum: 1
        }
    }
}, {
    $group: {
        _id: "$count",
        count: {
            $sum: 1
        }
    }
}])