How to find different field values in MongoDB collection using Node MongoClient
In my MEAN application, I need to find various values of a field named "DataFields" from my collection "Fixed_Asset_Register" using (non-mango) MongoClient:
var mongodb = require('mongodb');
var assert = require('assert');
var MongoClient = mongodb.MongoClient;
MongoClient.connect(url, function (err, db) {
if (err) {
console.log('Unable to connect to the mongoDB server. Error:', err);
} else {
console.log('Connection established to', url);
var collection = db.collection('Fixed_Asset_Register');
var distictDataFieldsValue = ?
}
What is the correct syntax to return individual values for a field named "DataFields"?
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I solved this problem using collection.distinct :
collection.distinct("DataFields",(function(err, docs){
console.log(docs);
assert.equal(null, err);
db.close();
}))
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You can also do this with an aggregation framework . A suitable aggregation pipeline would consist of a step that groups the document using a key and create an aggregated field that stores the documents generated by this grouping. The battery operator is for this . $group
DataFields
count
$sum
The next step in the pipeline is the operator, who then filters documents that have a 1 to show the difference. $match
count
The last operator in the pipeline then groups these individual items and adds them to the list using the operator. $group
$push
As a result, your aggregation will look like this:
var collection = db.collection('Fixed_Asset_Register'),
pipeline = [
{
"$group": {
"_id": "$DataFields",
"count": {"$sum": 1}
}
},
{
"$match": { "count": 1 }
},
{
"$group": {
"_id": 0,
"distinct": { "$push": "$_id" }
}
}],
result = collection.aggregate(pipeline).toArray(),
distictDataFieldsValue = result[0].distinct;
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