To update the documents in the collection through multiple methods like update(), updateOne(), updateMany() . it works like update row into table in RDBMS.
Syntax:-
> db.collectionName.update({whereCondition},{newData});
In RDBMS:-
update tableName set field1='Value1',field2='Value2' where conditions
Example:- Suppose, You have employees collection
[
{
"_id" : ObjectId("5fdc8b842649b8748d4ec107"),
"name" : "John",
"salary" : 100000
},
{
"_id" : ObjectId("5fdcdb87b6dad382104b0f86"),
"name" : "Rom",
"salary" : 50000
}
]
Now, you want to update employee salary where name is John.
> db.employees.update({name:"John"},{$set:{salary:200000}})
if the document is updated then show a message
WriteResult({ “nMatched” : 1, “nUpserted” : 0, “nModified” : 1 })
updateOne() method
this method is used to update only one document in the collection.
Syntax:-
> db.collectionName.updateOne({whereCondition},{newData});
Example:-
> db.employees.updateOne({name:"Rom"},{$set:{salary:70000}})
after update successfully then show message
{ “acknowledged” : true, “matchedCount” : 1, “modifiedCount” : 1 }
updateMany() method
This method is used to update multiple documents in the collection.
Syntax:-
> db.collectionName.updateMany({whereCondition},{newData})
save() method
This method is used to replace exists documents with the new document.
Syntax:-
> db.collectionName.save({whereCondition},{newData})
C# Dictionary – Interview Questions
Q 1: How do you update documents?
Ans: Use updateOne() or updateMany().
Q 2: What is $set operator?
Ans: It updates specific fields.
Q 3: How do you replace a document?
Ans: Use replaceOne().
Q 4: What is upsert?
Ans: Upsert inserts the document if it does not exist.
Q 5: Can multiple documents be updated?
Ans: Yes using updateMany().