1
00:00:02,160 --> 00:00:08,790
So after this useful piece of advice, let's now have a look at some dedicated array query selectors that

2
00:00:08,790 --> 00:00:11,220
can help us find the right query,

3
00:00:11,430 --> 00:00:13,410
let's start with size,

4
00:00:13,410 --> 00:00:15,440
size is pretty straightforward

5
00:00:15,780 --> 00:00:24,990
Now here in our collection, if we have a look at all our users, we can see that they all have the same

6
00:00:24,990 --> 00:00:28,460
amount of hobbies, they all have two hobbies.

7
00:00:28,560 --> 00:00:38,360
Now let's therefore add a new user with insertOne and that user will generally follow the scheme and

8
00:00:38,360 --> 00:00:39,410
have a name,

9
00:00:39,410 --> 00:00:41,600
whoops, we don't need to wrap that but we could,

10
00:00:41,630 --> 00:00:43,240
the name is Chris let's say

11
00:00:43,490 --> 00:00:47,800
and we can specify an age and the other parts that doesn't really matter,

12
00:00:47,810 --> 00:00:50,330
let's specify the hobbies that matters.

13
00:00:50,510 --> 00:00:58,120
And we can even use a different approach here and say sports, cooking and hiking, like this,

14
00:00:58,130 --> 00:01:01,290
so here I don't have embedded documents, I could add them,

15
00:01:01,310 --> 00:01:02,370
it really doesn't matter,

16
00:01:02,400 --> 00:01:05,620
to save time and space I'll just use strings.

17
00:01:05,690 --> 00:01:07,960
So now I have one new user in the database,

18
00:01:08,060 --> 00:01:15,190
Chris and now I want to find all users who have three hobbies which should be just Chris because the

19
00:01:15,230 --> 00:01:16,340
other users have two

20
00:01:16,430 --> 00:01:21,040
and it doesn't matter whether a hobby is an embedded document or just a string,

21
00:01:21,080 --> 00:01:28,340
it's just the amount of items in the hobbies array that matters. To find all users with exactly three

22
00:01:28,340 --> 00:01:41,130
hobbies, I can look into my users with find and now the value for find is that I use hobbies and I'm looking

23
00:01:42,650 --> 00:01:46,900
for a size of three, written like this.

24
00:01:47,150 --> 00:01:47,880
If I hit enter,

25
00:01:47,960 --> 00:01:49,570
I only find Chris.

26
00:01:49,730 --> 00:01:54,650
Now what's important to understand about this command by the way is that this has to be an exact number,

27
00:01:54,710 --> 00:01:59,750
you can't say give me anything with more than two items. If you need something like this,

28
00:01:59,900 --> 00:02:02,030
you'll have to retrieve your data differently,

29
00:02:02,030 --> 00:02:06,980
this is something mongodb does not support yet, you can only look for exact matches here.