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Now that we had a brief look at how we can query embedded documents and arrays,

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let me come back to my comparison selectors here.

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We had a look at most of them but we did not look at $in or $nin,

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now what do these two operators do? Now

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for that,

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let's come back to let's say the runtime. I'll reach out to my movies again and pretty print the results

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and the filter I'll specify here

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will check the runtime field

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and I want to make sure that the runtime is either 30 or 42. Now we know that in our dataset, I could

10
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achieve this with lower than or equal to 42 because we just happen to have data with 30, 42 and 60 minutes

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in there

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so this will give us all the items that have a runtime lower than or equal 42 which is all the items

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with 30 or 42

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but of course, that's not the case for every dataset and we might not even know that our data looks like

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that.

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So if we know there are two discrete values we want to check for,

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we can use $in operator. In takes an array and now this does not mean it looks for this array

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but in this array, we specify all the values that will be accepted as values for this key,

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so in our case 30 and 42.

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So it will find us all documents that have a runtime of 30 or 42 but not of 60

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or if we had 15 minutes, this would also be excluded.

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So if I now hit enter, we get back a bunch of results and you should only find runtime equal to 30 in there

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or a runtime equal to 42, like for this document. Now nin is just the opposite,

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we could say we want to find everything where the value is not in this range or this is not a range

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but in this set of values,

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so now we would find all values, all entries where the runtime is not equal to 30 or 42.

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So if I now hit enter in our dataset, this will now only include items with a runtime of 60 but again

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if you had more values there, like 15 minutes, 20 minutes, these would now also be included in our result

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set here.

30
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So that is in and not in, these two missing comparison operators.

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And with that we had a look at all comparison operators,

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so let's now move on to logical operators in the next module.