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So back in our mongo shell with the data I also worked on in the last modules.

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Now for what I'm showing you, you can use with any data you have,

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you don't need specific data.

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So here I happen to still have my users collection I worked with in the update module

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but again it's fine if you have different data or the same collection but the data looks different, that's

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all fine.

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Let's say we want to delete Chris, now

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to delete

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Chris, what you can do is you can use your collection and then use delete one if you know it'll be only

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one document you want to delete.

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Now you need to specify a query selector, a filter here and the filter you specify here is the same as

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for updating and finding documents,

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everything you learned in the read module will work here, whatever you need to identify a document, with

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how many conditions you might need is fine.

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If you check the age and the name and let's say the hobbies all in one query selection, that is fine,

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you can do that,

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you simply need to narrow down the document or the documents you want to delete.

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So a simple check is of course to look for 

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name equal to Chris and that is it,

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you can specify a second argument where you can set a write concern if you want to but this is not required

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if you're fine with the default write

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concern as I am for the rest of this course. So I can just hit enter

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and you see, one document was deleted

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and unsurprisingly if we now look into all users, we'll see Maria, Anna, Manuel and Max but Chris is

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gone.

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Now with Chris being gone and delete one being used,

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let me use delete many to delete all persons who are sporty and have the age greater than 30.

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So for this, we can again use our collection and then delete many

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because here I know I want to delete multiple records,

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this can still delete only one if only one record should match your condition

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but unlike delete one which will then only just delete the first record that matches, even if you had

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multiple documents that would match,

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this delete

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many will always delete all matching documents.

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So here I can say age should be greater than 30 and isSporty

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should be true,

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this is now my condition.

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If I hit enter,

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nothing was deleted

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so let's quickly check,

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well it's total age of course, not age,

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my bad,

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so let's quickly change this to total age and still, nothing was deleted.

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Well the reason for this is simple,

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we had no matching document.

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Maria is simply younger, Anna doesn't have an age, Manuel would have an age but is not sporty and Max is

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sporty but doesn't have an age.

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So what we can do is we can of course delete all persons who are sporty and where total

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age does not exist,

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so where exists is false,

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you learned about exists in the read section too.

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Now if I hit enter, two documents were deleted,

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so let's quickly have a look at our collection and

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we see Anna is still there because she doesn't have an age, she's sporty but she doesn't have an age

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and total age

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null as you learn then the read section does not suffice for exists

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false because the field does exist,

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it's null but it does exist.

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Manuel is also still there

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but Max and Maria were deleted because they were sporty and they had no age field

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by the looks of it.

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So this is delete many in action

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and as you see, here delete many taking into account two different query selectors,

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of course you can add as many as you need

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as I mentioned.