I have a schema similar to
{
'user_id' : 1,
'marks' : [10, 40]
}
I want to find the number of users who have scored marks between 20 and 30 at least once.
I tried the following query
db.users.count({
'marks' : {$gte: '20', $lt: '30'}
})
But this also included those with marks more than 30 ...
Use $elemMatch to constrain both parts of the range query to the same marks element:
db.users.count({
marks: {$elemMatch: {$gte: 20, $lt: 30}}
})
Isn't it just this:
db.scores.count( { 'marks' : { '$gt' : min_value , '$lt' : max_value } } )
Which in your case would translate to:
db.scores.count( { 'marks' : { '$gt' : 20 , '$lt' : 30 } } )
db.scores.count(
{ marks: { $elemMatch: { $gte: 20, $lt: 30} } }
)
For more information refer https://docs.mongodb.com/manual/reference/operator/query/elemMatch/
So assuming you had the following data in collection scores:
{ 'user_id' : 1, 'marks' : [ 10, 40 ] }
{ 'user_id' : 2, 'marks' : [ 5, 18 ] }
{ 'user_id' : 3, 'marks' : [ 15, 25 ] }
{ 'user_id' : 4, 'marks' : [ 22, 33 ] }
Then you would expect to filter user_ids 3 and 4, a count of 2.
The simplest way to run your query is to do:
db.scores.count({'marks':{$in: [20,21,22,23,24,25,26,27,28,29,30]}})
But not pretty...
with $and you can also write
db.scores.count({$and: [{"price": {$lt: 30}}, {"price": {$gte: 20}}]})
