Get Started with MongoDB
Update Mongo Documents arrays using $push, $pull and $each operations
In this lesson, we learn that updating arrays within MongoDB documents involves using the $push and $pull operators.
The $push operator allows us to add new items to an array, while combining it with the $each operator enables us to add multiple items simultaneously.
We demonstrate how to add "Java" and ".Net" to the skills array.
Conversely, the $pull operator removes elements from an array, and we can use the in operator with $pull to remove multiple items, such as "Python" and "SQL," based on specified criteria, providing flexibility in array manipulation.
[00:00] Let's modify update1 to updateMany. Now, this doesn't change much in our case, since we're just going to use the very same query, so there would be still one document that would be matched. However, what we want to do is to use a slightly different operator. And let's take a look at the skills array, since we haven't worked with arrays yet. So let's push something into the array.
[00:22] Now, again, we define what is the operation over here, and now we specify what is the property. This is skills. And let's say that we want our document to learn what is Kubernetes. So matched one, modified one. Let's see what is the find operation.
[00:39] And we've got Kubernetes over here. So let's also add some more properties. Now, the problem is that if we have passed more than one item over here, then it would not be iterated over the array, so we would not end up having 5 plus 2, that would be 7 new skills, but the whole array would be added as a sub array into the skills array. So what we should put here, let's just change it to something more relevant, let's say that would be Java and .NET. We need to wrap it again.
[01:17] So that would be push, that would be skills, right? But we cannot do it directly like this. So for this reason, we're going to, just as in any parts in Mongo, we're going to wrap it with another operator. In this case, this is going to be $each. So let's run it, let's see what Bob Johnson is, and we can see that it has been flattened.
[01:40] So push adds items into the array that is one of the properties on a document. Now if we want to remove something from the array, we pull it out from the array. So let's remove Kubernetes from the skills array and we would see that now all the skills are there except for Kubernetes. Or if we want to pull multiple things, now this is not going to be each but what we're going to do is that it should be the in operator because any of these that match the same as we've seen in previous lessons is going to be removed. So let's now remove Python and let's also remove SQL.
[02:25] So after this change, we would see that they're gone.