MongoDB - Update an object in nested Array

问题

{
  \"_id\": \"xPBc4By8FemDwTPqH\",
  \"u\": {
    \"_id\": \"6PoZawHZcQz4Gwzcv\",
    \"username\": \"michael\"
  },
  \"friends\": [
    {
      \"u\": {
        \"_id\": \"eGqDjAjjtYADbuSnn\",
        \"username\": \"michael\",
        \"name\": \"michael\"
      }
    },
    {
      \"u\": {
        \"_id\": \"k4gKCGwYryXDMMHvs\",
        \"username\": \"joyce\",
        \"name\": \"joyce\"
      }
    }
  ]
}

I want to update the name of \"friends.u.username\": \"michael\" \'s name is \"hello\", how I need to do it.

回答1:

Apply the $set operator together with the $ positional operator in your update to change the name field.

The $ positional operator will identify the correct element in the array to update without explicitly specifying the position of the element in the array, thus your final update statement should look like:

db.collection.update(
    { "friends.u.username": "michael" }, 
    { "$set": { "friends.$.u.name": "hello" } }
)

回答2:

You can use $set operator.

> db.test.update({"friends.u._id":"eGqDjAjjtYADbuSnn"},{$set:{"friends.$.u.name":"hello"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

回答3:

Below should work fine as its tested

First check the current value of the array.

db.test.findOne({"friends.u.id" : "eGqDjAjjtYADbuSnn"},{"friends.u.name":1})

Now fire the update command

db.test.update({"friends.u.id" : "eGqDjAjjtYADbuSnn"},{$set:{"friends.$.u.name":"hello"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Now check the results again to validate the update values

db.test.findOne({"friends.u.id" : "eGqDjAjjtYADbuSnn"},{"friends.u.name":1})

Hope this helps.

来源：https://stackoverflow.com/questions/34431435/mongodb-update-an-object-in-nested-array

标签

mongodb

updates