MongoDB CRUD Operation Update of embedded documents.
Example
For the following schema:
{name: 'Tom', age: 28, marks: [50, 60, 70]}
Update Tom's marks to 55 where marks are 50 (Use the positional operator $):
db.people.update({name: "Tom", marks: 50}, {"$set": {"marks.$": 55}})
For the following schema:
{name: 'Tom', age: 28, marks: [{subject: "English", marks: 90},{subject: "Maths", marks: 100}, {subject: "Computes", marks: 20}]}
Update Tom's English marks to 85 :
db.people.update({name: "Tom", "marks.subject": "English"},{"$set":{"marks.$.marks": 85}})
Explaining above example:
By using {name: "Tom", "marks.subject": "English"} you will get the position of the object in the marks array, where subject is English. In "marks.$.marks", $ is used to update in that position of the marks array
Update Values in an Array
The positional $ operator identifies an element in an array to update without explicitly specifying the position of the element in the array.
Consider a collection students with the following documents:
{ "_id" : 1, "grades" : [ 80, 85, 90 ] }
{ "_id" : 2, "grades" : [ 88, 90, 92 ] }
{ "_id" : 3, "grades" : [ 85, 100, 90 ] }
To update 80 to 82 in the grades array in the first document, use the positional $ operator if you do not know the position of the element in the array:
db.students.update(
{ _id: 1, grades: 80 },
{ $set: { "grades.$" : 82 } }
)
