I am trying to make a consultant on my MongoDB database:
What I want to do is to obtain some data that is integrated in a nested array and filter by one of this nested keys.
The document is the following:
[
{
"name": "PharmaMaria",
"country": "Spain",
"currency": "EUR",
"medicines": [
{
"name": "Medicine 1",
"type": "Suncream",
"price": 32,
},
{
"name": "Medicine 2",
"type": "Suncream",
"price": 5
},
{
"name": "Medicine 3",
"type": "Pills",
"price": 7
}
]
}
]
And I want to get something like this filtering by medicines.type
values = [
{
"name": "Medicine 1",
"price": 32
},
{
"name": "Medicine 2",
"price": 5
}
]
Here is the playground I created https://mongoplayground.net/p/_riatO8PKVp
Thanks!
You have to add a $project or $addFields stage and use $filter operator to apply the condition on each elements.
db.collection.aggregate([
{
"$match": {
"country": "Spain",
"medicines.type": "Suncream"
},
},
{
"$addFields": { // <- To add a new key
"medicines": { // <- Replacing existing `medicines` key
"$filter": { // <- Apply condition on each array elements
"input": "$medicines",
"as": "elem",
"cond": { // <- Applying match condition inside this block
"$eq": [
"$$elem.type",
"Suncream"
],
}
}
}
}
},
])
To get Only specific keys from array, use $map
db.collection.aggregate([
{
"$match": {
"country": "Spain",
"medicines.type": "Suncream"
},
},
{
"$addFields": {
"medicines": {
"$map": {
"input": {
"$filter": {
"input": "$medicines",
"as": "elem",
"cond": {
"$eq": [
"$$elem.type",
"Suncream"
],
}
}
},
"as": "med",
"in": {
"name": "$$med.name",
"price": "$$med.price",
}
},
}
}
},
])