My MongoDB collection with sample data is attached with the screenshot below
I want to fetch rows by passing grade value and the resulting records should be returned as follows
case 1: when grade = 12, Row 1,3,6 and 7 should be returned ie given
grade 12 should compare with gradeFrom and gradeTo
case 2: when grade = 1, Row 5 should returned
As a summary of above cases, the given grade should be greater than or equal to gradeFrom AND less than or equal to gradeTo.
The mongoose query that I used is given below, but the data returned is empty in my code
let andCondition = [];
let grade = 12;
andCondition.push({ gradeFrom: {$gte: grade}});
andCondition.push({ gradeTo: {$lte: grade}});
let data = await Course.find({$and :andCondition});
console.log(andCondition) gives the below object
[
{ gradeFrom: { '$gte': 12 } },
{ gradeTo: { '$lte': 12 } }
]
Please help me to get this done.
You have reversed the range logic.
In Math, it should be:
gradeFrom <= grade <= gradeTo
While in MongoDB query:
{ gradeFrom: { $lte: grade } }
{ gradeTo: { $gte: grade } }
Related
Basically I have documents in which I have on field called "Difficulty Level" and value of this filed is between 1 to 10 for each documents.
So, I have to select random 10 or 20 documents so that in randomly selected documents , atleast 1 document should be there for each difficulty level i.e. from 1 to 10. means there should atlease one document with "Difficulty level" : 1 ,"Difficulty level" : 2 ,"Difficulty level" : 3 ............."Difficulty level" : 10.
So, How can I select documents randomly with this condition fulfilled ?
Thanks
I tried $rand operator for selecting random documents but can't getting solution for that condition.
If I've understood correctly you can try something like this:
The goal here is to create a query like this example
This query gets two random elements using $sample, one for level1 and another for level2. And using $facet you can get multiple results.
db.collection.aggregate([
{
"$facet": {
"difficulty_level_1": [
{
"$match": { "difficulty_level": 1 } },
{ "$sample": { "size": 1 } }
],
"difficulty_level_2": [
{ "$match": { "difficulty_level": 2 } },
{ "$sample": { "size": 1 } }
]
}
}
])
So the point is to do this query in a dynamic way. So you can use JS to create the object query an pass it to the mongo call.
const random = Math.floor((Math.random()*10)+1) // Or wathever to get the random number
let query = {"$facet":{}}
for(let i = 1 ; i <= random; i++){
const difficulty_level = `difficulty_level_${i}`
query["$facet"][difficulty_level] = [
{ $match: { difficulty_level: i }},
{ $sample: { size: 1 }}
]
}
console.log(query) // This output can be used in mongoplayground and it works!
// To use the query you can use somethiing like this (or other way you call the DB)
this.db.aggregate([query])
I have the below snippet from a JSON Object that has 3,500 records in it.
[
{
"use:firstName": "Bob",
"use:lastName": "Smith",
"use:categoryId": 36,
"use:company": "BobSmith",
"use:webExId": "Bob.Smith#email.com",
"use:address": {
"com:addressType": "PERSONAL",
"com:city": "US-TX",
"com:country": 1
}
},
{
"use:firstName": "Jane",
"use:lastName": "Doe",
"use:categoryId": 36,
"use:webExId": "Jane.Doe#email.com",
"use:address": {
"com:addressType": "PERSONAL",
"com:city": "US-CA",
"com:country": "1_1"
}
}
{
"use:firstName": "Sam",
"use:lastName": "Sneed",
"use:categoryId": 36,
"use:webExId": "Sam.Sneed#email.com",
"use:address": {
"com:addressType": "PERSONAL",
"com:city": "US-CA",
"com:country": "1_1"
}
}
]
I am using NodeJS and I have been stuck on figuring out the best way to:
1. Iterate through ['use:address']['com:city' to map out and identify all of the Cities. (In the example above, I have two: US-TX and US-CA in the three records provided)
2. Then identify how many records match each City (In the example above, I would have US-TX: 1 and US-CA: 2)
The only code I have is the easy part which is doing a forEach loop through the JSON data, defining userCity variable (to make it easier for me) and then logging to console the results (which is really unnecessary but I did it to confirm I was looping through JSON properly).
function test() {
const webexSiteUserListJson = fs.readFileSync('./src/db/webexSiteUserDetail.json');
const webexSiteUsers = JSON.parse(webexSiteUserListJson);
webexSiteUsers.forEach((userDetails) => {
let userCity = userDetails['use:address']['com:city'];
console.log(userCity);
})
};
I've been searching endlessly for help on the topic and probably not formulating my question properly. Any suggestions are appreciated on how to:
1. Iterate through ['use:address']['com:city' to map out and identify all of the Cities.
2. Then identify how many records match each City (In the example above, I would have US-TX: 1 and US-CA: 2)
Thank you!
You could reduce the webexSiteUsers array into an object that is keyed by city, where each value is the number of times the city occurs. Something like the below should work.
const counts = webexSiteUsers.reduce((countMemo, userDetails) => {
let userCity = userDetails['use:address']['com:city'];
if (countMemo[userCity]) {
countMemo[userCity] = countMemo[userCity] + 1;
} else {
countMemo[userCity] = 1;
}
return countMemo;
}, {});
counts will then be an object that looks like this.
{
"US-TX": 1,
"US-CA": 2
}
Given a collection with lets say 1.000.000 entries and each of them have their own unique property called number which is indexed. How can I efficiently find the lowest gap in the number sequence.
An easy example would be a sequence of indexes like: 1,2,3,4,6,7,10, where I would like to get back the number 5 since this will be the lowest missing number in the sequence.
Is there a possible way (maybe aggregation) without the need to query all numbers.
One way of doing this would be with a cursor. With a cursor, you can manually iterate through the documents until you find one that matches your criteria.
var cursor = db.coll.find({}).sort({number: 1});
var prev = null
while (cusor.hasNext()) {
var curr = cursor.getNext()
if (prev && prev.number + 1 !== curr.number) break;
prev = curr;
}
One is get all the numbers and find the ones missing between them.
An aggregate example that you can use to not have to get them all. https://www.mongodb.com/community/forums/t/query-to-find-missing-sequence/123771/2
// Assuming the sample data with sequence numbers from 1 thru 10 as follows:
{ id: 1 },
{ id: 2 },
{ id: 4 },
{ id: 7 },
{ id: 9 },
{ id: 10 }
// And, note the missing numbers are 3, 5, 6 and 8. You can use the following aggregation to find them:
db.collection.aggregate([
{
$group: {
_id: null,
nos: { $push: "$id" }
}
},
{
$addFields: {
missing: { $setDifference: [ { $range: [ 1, 11 ] }, "$nos" ] }
}
}
])
Below is my sample JSON object. I want to get the 'title' value based
on the longitude value. I have multiple(20-30) longitudes to get the titles, so I don't want to loop through those many times:
{
items:[
{
longitude:-72.897668,
latitude:40.453576,
title:52 street
},
{
longitude:-71.897668,
latitude:41.453576,
title:5th Ave
}
]
}
Can anyone suggest me how to get value without using for-loops.
Did you try something linke array.filter()?
function filterByLongitude(element) {
var expected = -72.897668
return element.longitude === expected;
}
var items = [{
longitude:-72.897668,
latitude:40.453576,
title:'52 street'
}, {
longitude:-71.897668,
latitude:41.453576,
title: '5th Ave'
}];
var match = items.filter(filterByLongitude);
console.log(match[0].title); // 52 street
I have a campaign collection, which is for advertisers. It's schema is:
var campaignSchema = new mongoose.Schema({
name: String,
sponsor: String,
[...]
target: {
age: {
lower: Number,
upper: Number
},
gender: String,
locations: Array, // [ { radius: '', lon: '', lat: '' } ]
activities: Array
}
});
I need to run a query with a specific age, and return all campaigns where that age is between age.lower and age.higher.
I have read the docs for $gt and $lt, however they appear to only work one way (so I could specify a range and match a value, however I need to specify a value and match a range).
Any suggestions?
Sorry I misunderstood the problem, I got it now.
db.collection.find( { "age.lower": { $lt: value1 }, "age.upper": { $gt: value1 } } );
So, for example, if your range is 25 to 40, and value1 is 30, 25 < 30 and 40 > 30 -- match!
If you use the same range with 20, 25 !< 20 -- will not match.
You could first create a query on the lower bound of that value, sort the results in descending order and get the top document from the result. Compare that document with the upper bound, if there is a match then that document has a range which contains that age. For example:
var age = 23;
var ads = db.campaign.find({ "age.lower": {"$lte": age } }).sort({"age.lower": -1}).limit(1);
if (ads != null) {
var result = ads[0];
if (result.age.upper > age) {
return result;
} else {
return null;
}
}