Lets learn how to use $inc operator with update() method in MongoDB.
test database, names collection
1 2 3 4 5 6 7 8 9 10 11 12 | > db.names.find().pretty()
{
"_id" : ObjectId("53c3fc2005e0ce2719d91bd2"),
"Company" : "Google",
"No" : 1
}
{
"_id" : ObjectId("53c3fd3bb9ae26fa217b1e12"),
"Company" : "Apple",
"Product" : "iPhone",
"No" : 2
} |
Here we have 2 documents. And we’ll be working on first document to illustrate the working of $inc operator.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | > db.names.update({"Company": "Google"}, {$inc: {"No": 2}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{
"_id" : ObjectId("53c3fc2005e0ce2719d91bd2"),
"Company" : "Google",
"No" : 3
}
{
"_id" : ObjectId("53c3fd3bb9ae26fa217b1e12"),
"Company" : "Apple",
"Product" : "iPhone",
"No" : 2
} |
Here “No” field will be incremented by 2. So the final value of “No” field is 3 (1+2).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | > db.names.update({"Company": "Google"}, {$inc: {"Sl_no": 1}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{
"_id" : ObjectId("53c3fc2005e0ce2719d91bd2"),
"Company" : "Google",
"No" : 3,
"Sl_no" : 1
}
{
"_id" : ObjectId("53c3fd3bb9ae26fa217b1e12"),
"Company" : "Apple",
"Product" : "iPhone",
"No" : 2
} |
If we apply $inc operator on an non-existing field, it will be created with the increment value itself.
Increment($inc) operator: MongoDB
[youtube https://www.youtube.com/watch?v=LjJJOY4DLMs]
YouTube Link: https://www.youtube.com/watch?v=LjJJOY4DLMs [Watch the Video In Full Screen.]
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | > db.names.update({"Company": "Google"}, {$inc: {"No": 1}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{
"_id" : ObjectId("53c3fc2005e0ce2719d91bd2"),
"Company" : "Google",
"No" : 4,
"Sl_no" : 1
}
{
"_id" : ObjectId("53c3fd3bb9ae26fa217b1e12"),
"Company" : "Apple",
"Product" : "iPhone",
"No" : 2
} |
Here we increment the value of “No” once again by 1. So the final value of “No” field is 4 (3+1).