Question 1:

Find the total number of item quantity (use TotalQty as alias) for customers having customerName as "abc" and "xyz". Sort the result in descending order of "TotalQty".

Output Format:

Each output document of the above query should look like the sample given below:

{"_id":"abc","TotalQty":9}

{"_id":"xyz", "TotalQty":99}

CodePudding user response：

Making the assumption that your documents contains a TotalQty field, and also some other additional fields that you want to strip out:

[
  {
    "_id": "Aaron",
    "fieldB": "ABC",
    "TotalQty": 99
  },
  {
    "_id": "Charles",
    "fieldB": "ABC",
    "TotalQty": 9
  },
  {
    "_id": "Brian",
    "fieldB": "Another",
    "TotalQty": 999
  }
]

Running a query like this:

db.collection.aggregate([
  {
    $sort: {
      "TotalQty": -1
    }
  },
  {
    $project: {
      _id: 1,
      TotalQty: 1
    }
  }
])

To give you results like this:

[
  {
    "TotalQty": 999,
    "_id": "Brian"
  },
  {
    "TotalQty": 99,
    "_id": "Aaron"
  },
  {
    "TotalQty": 9,
    "_id": "Charles"
  }
]

Info:

• Aggregate command
• $sort
• $project

You haven't mentioned in your question about summing a list of products, but you could do it like this: Need to sum from array object value in mongodb

Example code:

• https://mongoplayground.net/p/YrFBZ0XV5AI

CodePudding user response：

I hope this is what you're expecting?

https://mongoplayground.net/p/AKy-_NaCBUo