MongoDB count different values in multiple arrays

Question

I want to count how often a unique value occurs. I have multiple arrays with objects like:

{“value”:”a”,”begin”:0,”end”:12}

but I only need the “value” part of the object so I projected only the values so the result of my projection looks like this but with multiple arrays:

{“values”:[{“value”:”a”},{“value”:”b”},{“value”:”b”}]}

My goal is to get a result array with all different values and how often they occurred in all multiple arrays:

[{“value”:”a”,”count”:1},{“value”:”b”,”count”:2}]

i dont know where my error is but i cant unwind the arrays. Would it be {$unwind: {path: "values"}? — Herakles
– Herakles, Commented Sep 19, 2022 at 13:20
You can use {$unwind: "$values"}. Please provide few sample documents and I'll show you — nimrod serok
– nimrod serok, Commented Sep 19, 2022 at 14:12
For example i would get 2 Documents with following data. { "values": [ "value": "a", "value": "b", "value": "c", "value": "a", "value": "b", "value": "c" ] } { "values": [ "value": "a", "value": "b", "value": "d", "value": "g", "value": "d", "value": "c" ] } And as result i need: { {"value": "a", "count": 3}, {"value": "b", "count": 3}, {"value": "c", "count": 3}, {"value": "d", "count": 2}, {"value": "g", "count": 1}, } — Herakles
– Herakles, Commented Sep 19, 2022 at 14:37

nimrod serok · Accepted Answer · 2022-09-19 14:49:36Z

1

You can simply do:

db.collection.aggregate([
  {$unwind: "$values"},
  {$group: {_id: "$values.value", count: {$sum: 1}}}
])

See how it works on the playground example

answered Sep 19, 2022 at 14:49

nimrod serok

16.1k2 gold badges15 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

MongoDB count different values in multiple arrays

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related