mongodb find documents using condition and update another field in the respective document

Question

I want to find any document in my collection that:

its hobby field is empty
or its hobby field doesn't exist

and then set the value of its hobby field to be equivalent of its sports field.

 db.myCollection.update(
            { $or: [{"hobby": {$exists: false} },{"hobby": ""}]}
        , {
            $set: {
                hobby: ????sports
            }
        }, {
            multi: true
        },
        function(err, result) {
            console.log(result);
            console.log(err);
        })

With this command above, I suppose I will be passing the value of sports as fixed value to all matching documents. is there any way to pick up its corresponding sports value and set it to hobby?

Possible duplicate of [Update MongoDB field using value of another field](https://stackoverflow.com/questions/3974985/update-mongodb-field-using-value-of-another-field) — Robert, Dec 17 '17 at 13:20

Kerumen · Answer 1 · 2017-12-18T14:55:02.610

0

You have to do this in 2 queries:

db.myCollection.find({ 
  $or: [{ "hobby": { $exists: false } }, { "hobby": "" }]
}).toArray().forEach(function (item) {
    db.myCollection.update(
      { _id: item._id },
      { $set: { hobby: item.sports } },
      { multi: true }
    )
  })
})

edited Dec 18 '17 at 14:55

answered Dec 17 '17 at 13:20

Kerumen

4,193
2
19
33

score 0 · Answer 2 · answered Dec 17 '17 at 14:32

here is the modified version that updates correctly the values:

   db.myCollection.find({ 
      $or: [{ "hobby": { $exists: false } }, { "hobby": "" }]
    }).toArray().forEach(function (item) {
        db.myCollection.update(
          { _id: item._id },
          { $set: { hobby: item.sports } },
          { multi: true }
        )
      })
    })

mongodb find documents using condition and update another field in the respective document

2 Answers2