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So now that we've covered how you might create new documents and new collections into our database using
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Mongoose and we also in the last lesson looked at how you might validate new data that's being entered
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into the database,
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now I want to cover the last parts of CRUD and briefly show you how you might update and delete data
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using Mongoose.
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If you remember previously we added in that Peach but we forgot to add an a name for it.
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This was allowed to happen because we didn't have the validation in place yet, we didn't set the name
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field as required
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when this happened.
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Let's use this opportunity to learn about how you would update data and let's give that document a name
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of Peach. I'm going to comment out my fruit.safe and down here just below the find
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we're going to update our peach.
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So we're going to again tap into that fruits collection through the fruit model and we're going to call
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the method updateOne.
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The reason I know how to do this is again because of the documentation. Inside the API documentation
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for all of our models
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you can see there's findOne,
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there's also update, update
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Many and updateOne. You can use all three of these depending on what you need
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but the one that I've chosen is updateOne and it has three required parameters and one optional parameter.
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What we have to specify is the condition to filter upon, so which document do you want to update basically.
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And then the next one is what are you going to update.
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And finally it accepts a callback which allows us to log any errors if there are any. Inside our code
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here
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we've called fruit.updateOne and now we're going to specify our first parameter which is going to
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be the filter or what it is that we want to update.
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In our case, I want to update the record that has a particular ID
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and I can see that ID in my Mongo shell and it's this string over here which was generated automatically
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when we created this document. And that ID corresponds to the document that has the peach without a name.
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So if I copy that over and I paste it in here then I now have my query.
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So this is the item that I want to update.
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It has an ID that is specific to it
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and it's this. The next thing that I can add is what it is that I want to update about it.
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In this case I'm going to update the name field and I'm going to set it to Peach.
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And finally the third parameter is simply going to be a callback function which will log any errors
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if there are any.
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So if error, then we'll log the error
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but if there weren't any errors, then we'll just log "Successfully updated the document".
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Now let's close everything off and hit save and let's go into our hyper terminal and run on node app.
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js
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again with that update and you can see now it says "Successfully updated the document"
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and if we go over to our Mongo shell and we look at all the fruits inside our fruit database, you can
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see that we don't have any extra documents.
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We've still only got five.
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But this last one now has the name field filled and it now has the value of Peach.
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So now if we run it again and it logs all of our fruits, you can see we now have apple, kiwi, orange, banana
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and peach.
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All of our data is now updated and complete. Over here
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you might see that the field Peach got added in right at the end to this document but the order doesn't
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actually matter because we can tap into every single property using the dot notation.
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So it'll search through this entire document and find the relevant piece of data for you just by writing
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that fruit
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.name. The final thing that we want to do is what if we wanted to delete a particular record.
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Let's say I'm going to delete this peach after all.
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Well then we could use the deleteOne method.
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I'm going to leave this as a challenge for you. Based off this documentation
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I want you to delete the peach entry in our fruits collection. If you succeed
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when I run in my Mongo shell the same fruits.find I should no longer see this last record.
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Pause the video now and see if you can complete this challenge.
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They've actually very helpfully included an example for you to show you how you might call this delete
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One function. And it only has two parameters:
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one is the conditions.
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This is again what exactly do you want to delete.
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You need it to match with something right> And then the second one is a callback.
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Again this allows us to log any errors that occurred when we were deleting the document.
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Let's implement that in our code.
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So I'm going to comment out our updateOne
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and just below it I'm going to say fruit.deleteOne. And the first parameter is of course the condition,
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what do I want to delete.
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Well I want to delete the document that has a name of Peach. You can also use the ID or anything else
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that's unique about it,
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but in this case I know that I have a document that's called Peach.
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Next I'm going to specify the callback function which only has an error as a parameter.
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And again I'm going to check if there was an error,
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I will flag the error but if there were no errors then I'm going to log successfully.
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"Successfully deleted the document".
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Now let's go ahead and run this code in our hyper terminal and see what happens.
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So now we've got successfully "delted" the
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document, a typo there from me.
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But when it loops through our data to find all of the documents, we no longer have a peach being shown.
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And again if I switch over to my Mongo shell and run db.fruits.find we now only have four
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entries with that last one where the name matches Peach being deleted.
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The other function that we might want to use is to deleteMany because sometimes you might want to just
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clear out a collection or delete a number of documents that match a particular condition.
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If you remember previously when we were running our app.js, for a couple of times we didn't actually
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comment out the person.save.
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And that means that every time we ran app.js, we created that same person John who's 37, got saved
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into our database many many times. If you head over to your Mongo shell and you wrote "show collections"
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you can see we have our fruits and our people.
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And if you say "db.people.find" to show us all the data in there, we have loads of Johns who are
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37. As a challenge
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I want you to delete all of the data in here where the name matches with John and I want you to clear
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out this collection
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through the use of this deleteMany method. Pause the video and try to complete the challenge.
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This is the syntax that we need to follow.
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We're going to tap into a particular model and we're going to call the deleteMany method. And then we're
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going to pass in the required two parameters which is the condition which matches the document we want
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to delete and the callback to log any errors. Down here let's comment out our deleteOne and instead let's
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now tap into the people's collection by typing person which is the name of the model that is linked
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to the people's collection. Person
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.deleteMany
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and then the first parameter is of course the condition.
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So we said that the name has to match John.
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And then the second parameter was just a callback with an arrow
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and if there was an error log the error
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else log "Successfully deleted
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all the documents".
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Now let's run this code and clear out our collection.
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So" successfully deleted all the documents" documents.
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And now if we do db.people.find again, you can see it's completely empty.
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We've deleted all of these records where the name matches with John. To ensure that we only have one
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John
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let's go ahead and save a single one of these.
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And now we should have a single John in our records
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and now let's comment this out again before we start adding more Johns into our people's collection.