db.Employee.update(
{"Employeeid" : 1},
{$set: { "EmployeeName" : "NewMartin"}});

1	db.coll.update({"_id": 1}, {"year": 2016}) // WARNING! Replaces the entire document
2	db.coll.update({"_id": 1}, {$set: {"year": 2016, name: "Max"}})
3	db.coll.update({"_id": 1}, {$unset: {"year": 1}})
4	db.coll.update({"_id": 1}, {$rename: {"year": "date"} })
5	db.coll.update({"_id": 1}, {$inc: {"year": 5}})
6	db.coll.update({"_id": 1}, {$mul: {price: NumberDecimal("1.25"), qty: 2}})
7	db.coll.update({"_id": 1}, {$min: {"imdb": 5}})
8	db.coll.update({"_id": 1}, {$max: {"imdb": 8}})
9	db.coll.update({"_id": 1}, {$currentDate: {"lastModified": true}})
10	db.coll.update({"_id": 1}, {$currentDate: {"lastModified": {$type: "timestamp"}}})
11
12	// Array
13	db.coll.update({"_id": 1}, {$push :{"array": 1}})
14	db.coll.update({"_id": 1}, {$pull :{"array": 1}})
15	db.coll.update({"_id": 1}, {$addToSet :{"array": 2}})
16	db.coll.update({"_id": 1}, {$pop: {"array": 1}}) // last element
17	db.coll.update({"_id": 1}, {$pop: {"array": -1}}) // first element
18	db.coll.update({"_id": 1}, {$pullAll: {"array" :[3, 4, 5]}})
19	db.coll.update({"_id": 1}, {$push: {scores: {$each: [90, 92, 85]}}})
20	db.coll.updateOne({"_id": 1, "grades": 80}, {$set: {"grades.$": 82}})
21	db.coll.updateMany({}, {$inc: {"grades.$[]": 10}})
22	db.coll.update({}, {$set: {"grades.$[element]": 100}}, {multi: true, arrayFilters: [{"element": {$gte: 100}}]})
23
24	// Update many
25	db.coll.update({"year": 1999}, {$set: {"decade": "90's"}}, {"multi":true})
26	db.coll.updateMany({"year": 1999}, {$set: {"decade": "90's"}})
27
28	// FindOneAndUpdate
29	db.coll.findOneAndUpdate({"name": "Max"}, {$inc: {"points": 5}}, {returnNewDocument: true})
30
31	// Upsert
32	db.coll.update({"_id": 1}, {$set: {item: "apple"}, $setOnInsert: {defaultQty: 100}}, {upsert: true})
33
34	// Replace
35	db.coll.replaceOne({"name": "Max"}, {"firstname": "Maxime", "surname": "Beugnet"})
36
37	// Save
38	db.coll.save({"item": "book", "qty": 40})
39
40	// Write concern
41	db.coll.update({}, {$set: {"x": 1}}, {"writeConcern": {"w": "majority", "wtimeout": 5000}})

// db.Employee.update() is deprecated
db.Employee.updateMany(
{"Employeeid" : 1},
{$set: { "EmployeeName" : "NewMartin"}});

//insert:
db.members.insert({'user_id':1,'name':'nanhe'})
//update :
db.members.update({'title':'MongoDB Overview'},{$set:{'title':'New MongoDB Tutorial'}})

db.people.updateMany( { age: { $gt: 25 } }, { $set: { status: "C" } }
)
--SQL
UPDATE people
SET status = "C"
WHERE age > 25

db.collectionName.update({"aField":"vale1"},{$set:{"anotherField":"value2"}})
-search for documentations for more examples than search
-aField is used to find the documents
-anotherField is the field that will be updated
-You can also use the below:
-- updateOne
-- findOneAndUpdate