MongoDB concatenate strings from two fields into a third field

Question

How do I concatenate values from two string fields and put it into a third one?

I\'ve tried this:

db.collection.update(
  { \"_id\": { $exists: true          


        

Answer 1

You can also follow the below.

db.collectionName.find({}).forEach(function(row) { 
    row.newField = row.field1 + "-" + row.field2
    db.collectionName.save(row);
});