Merge two array field in mongoDB

Question

I have a collection of the following structure

{
   _id : ObjectId(\"52f0795a58c5061aa34d436a\"),
   \"attribute1\" : [1, 3, 6, 7],
   \"attribute2\" : [2, 4         


        

Answer 1

Using the .aggregate() method and the $setUnion operator.

db.collection.aggregate([
    { "$project": { 
        "attribute3": { "$setUnion": [ "$attribute1", "$attribute2" ] } 
    }}
])

Which yields:

{
    "_id" : ObjectId("52f0795a58c5061aa34d436a"),
    "attribute3" : [8, 4, 2, 6, 3, 7, 1]
}