MongoDB query document that doesn't have a given entry? - mongodb

Question

I have the following document:
{
"address": {
"building": "1007",
"coord": [ -73.856077, 40.848447 ],
"street": "Morris Park Ave",
"zipcode": "10462"
},
"borough": "Bronx",
"cuisine": "Bakery",
"grades": [
{ "date": { "$date": 1393804800000 }, "grade": "A", "score": 2 },
{ "date": { "$date": 1378857600000 }, "grade": "A", "score": 6 },
{ "date": { "$date": 1358985600000 }, "grade": "A", "score": 10 },
{ "date": { "$date": 1322006400000 }, "grade": "A", "score": 9 },
{ "date": { "$date": 1299715200000 }, "grade": "B", "score": 14 }
],
"name": "Morris Park Bake Shop",
"restaurant_id": "30075445"
}
I want a query that looks at the grades.grade and grades.score and doesn't return a this document if a grades object has grade == "A" AND score == 2. However, I want it to return a document if for example one grades object has grade == "A" and another grades object has score == 2.
This might also illustrate what I'm trying to do (although it doesn't work):
db.restaurants.find({
grades : {
$and: [
{"grade": {'$ne':"A"}},
{"score": {'$ne':2}}
]
}
});

Answer 1

You can try below query.
You basically require $anding $or and $nand. MongoDB doesn't have $nand operator, so I replaced it with the equivalent experession.
db.restaurants.find({
$and: [{
$or: [{
"grades.grade": "A"
}, {
"grades.score": 2
}]
}, {
$nor: [{
$and: [{
"grades.grade": "A"
}, {
"grades.score": 2
}]
}]
}]
});
$or operation will match all documents where any of the grade embedded document has either grade A or score is 2.
{ "grade": "A", "score": 3 } --- Just grade A
{ "grade": "A", "score": 2 } --- Both grade A and score 2
{ "grade": "B", "score": 2 } --- Just score 2
$nand operation will match all the documents where none of the grade embedded documents has both grade as A and score is 2
{ "grade": "A", "score": 3 } --- Just grade A
{ "grade": "B", "score": 2 } --- Just score 2
{ "grade": "C", "score": 4 } --- None
$and of above operations is the intersection.
{ "grade": "A", "score": 3 } --- Just grade A
{ "grade": "B", "score": 2 } --- Just score 2