The basic operation of MongoDB update does not exist data

Finding data with Y as 100

Db.test_collection.find ({y:100})

Found no, this time update y to 100 data to Y 999

Db.test_collection.update ({y:100},{y:999})

We'll look at the data for Y 999.

Db.test_collection.find ({y:999})

Found not present

We sometimes have this need, when updating a nonexistent data, automatically created, this is the third parameter of update, if true, indicates that if the data found does not exist, it will automatically create a

Db.test_collection.update ({y:100},{y:999},true)

When we look at the data for Y 999, we have

Db.test_collection.find ({y:999})

The basic operation of MongoDB update does not exist data