Display a only one field if duplicate named field are present in mongodb

Question

Below is the Collection

prac> db.Inventory4.find()
[
  {
    _id: ObjectId("631329cffebe4eb8a30054b1"),
    item: 'journal',
    instock: [ { warehouse: 'A', qty: 5 }, { warehouse: 'C', qty: 15 } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b2"),
    item: 'notebook',
    instock: [ { warehouse: 'C', qty: 5 } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b3"),
    item: 'paper',
    instock: [ { warehouse: 'A', qty: 60 }, { warehouse: 'B', qty: 15 } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b4"),
    item: 'planner',
    instock: [ { warehouse: 'A', qty: 40 }, { warehouse: 'B', qty: 5 } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b5"),
    item: 'postcard',
    instock: [ { warehouse: 'B', qty: 15 }, { warehouse: 'C', qty: 35 } ]
  }
]

Result of query is

prac> db.Inventory4.find({"instock.warehouse":{$eq: "A"}}, {"item":true, "instock.warehouse":1})
[
  {
    _id: ObjectId("631329cffebe4eb8a30054b1"),
    item: 'journal',
    instock: [ { warehouse: 'A' }, { warehouse: 'C' } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b3"),
    item: 'paper',
    instock: [ { warehouse: 'A' }, { warehouse: 'B' } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b4"),
    item: 'planner',
    instock: [ { warehouse: 'A' }, { warehouse: 'B' } ]
  }
]

My question is why are other warehouses printed along with A ? My real task was "Write a query to display item field,quantity field whose warehouse status is 'A'"

what is the expected output in json? You query will return all the document un-changed if at least one member of the array is `instock.warehouse=A` — Takis, Sep 03 '22 at 11:33

score 0 · Answer 1 · answered Sep 03 '22 at 11:47

If what you are trying to do is to get result like this one below:

[
  {
    _id: ObjectId("631329cffebe4eb8a30054b1"),
    item: 'journal',
    instock: [ { warehouse: 'A', qty: 60  } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b3"),
    item: 'paper',
    instock: [ { warehouse: 'A', qty: 40  } ]
  },
  {
    _id: ObjectId("631329cffebe4eb8a30054b4"),
    item: 'planner',
    instock: [ { warehouse: 'A', qty: 5  } ]
  }
]

you can read this answer and get clear understanding according to your mongodb version.

Display a only one field if duplicate named field are present in mongodb

1 Answers1