mongoose query where id not in other model - mongodb

Question

so I have this kind of model
const vetSchema = new mongoose.Schema({
username: {type: String, required: true, trim: true, unique: true},
email: {type: String, unique: true, trim: true,},
expYear: {type: Number},
KTP: {type: String, unique: true, trim: true},
cert_id: {type: String, unique: true, trim: true, select: false},
})
const clinicSchema = new mongoose.Schema({
vet: [{type: mongoose.Schema.Types.ObjectID, ref: 'vet'}],
)}
what I want to do is finding vet by username, which the vet ID is not included in the clinic based on clinic ID, the query to find the vet is {username: {$regex: (?i)${keyword}.*}}
for example, we have this data
Clinic = [{
"_id" : ObjectId("5e57a45836d300b188f4444a"),
"vet": [ObjectId("5e0742fc9d4b20100f89b626"),ObjectId("5e53698fd2b9ee43e7693e01")]
}]
Vet = [
{
"_id" : ObjectId("5e0742fc9d4b20100f89b626"),
"username": "VetClinic"
},
{
"_id" : ObjectId("5e55df62576bc9811877033e"),
"username": "VetNotClinic"
},
{
"_id" : ObjectId("5e53698fd2b9ee43e7693e01"),
"username": "VetClinic"
},
]
what i want is if I find Vet it only shows VetNotClinic because VetClinic is included in the clinic's ID, any good query / agregate?

Answer 1

you can use $nin to query where a field is "not in" an array like so
Vet.find({
username: {$regex: (?i)${keyword}.*},
_id: {$nin: clinic.vet}
})