1
00:00:02,160 --> 00:00:04,120
That's it for this module,

2
00:00:04,320 --> 00:00:10,080
we had a detailed look at databases collections and documents and what all these things are. That a database

3
00:00:10,080 --> 00:00:14,040
holds multiple collections and each collection can then hold multiple documents,

4
00:00:14,040 --> 00:00:20,110
this is how mongodb structures its data. Databases and collections are created lazily,

5
00:00:20,130 --> 00:00:26,920
that means only when a document is inserted, only when you need a specific database or collection. A

6
00:00:26,910 --> 00:00:29,550
document can't directly be inserted into a database,

7
00:00:29,550 --> 00:00:31,190
it's always part of a collection,

8
00:00:31,200 --> 00:00:37,070
so keep that layered architecture in mind. Documents have a certain structure,

9
00:00:37,350 --> 00:00:41,700
each document needs a unique ID which has to be called _id,

10
00:00:41,730 --> 00:00:48,000
you can set this on your own or take the one mongodb creates for you and you can have embedded documents

11
00:00:48,090 --> 00:00:54,390
as well as arrays as well as texts, numbers, all the other data types you already saw and we'll dive in later

12
00:00:54,450 --> 00:00:56,220
in this course.

13
00:00:56,400 --> 00:01:02,850
An important part or aspect of working with a database is that you can perform crud operations,

14
00:01:02,850 --> 00:01:06,350
that stands for create, read, update and delete.

15
00:01:06,380 --> 00:01:12,030
Mongodb offers multiple crud operations for a single document and bulk actions, you can insert one element

16
00:01:12,060 --> 00:01:18,240
or one document or many documents and you can find many documents or find one document.

17
00:01:18,300 --> 00:01:24,920
Some methods require arguments, insertOne for example needs to know what you want to insert, other methods

18
00:01:24,930 --> 00:01:31,990
like find can use arguments as you will see and as you already saw in this module but don't need one.

19
00:01:32,710 --> 00:01:33,680
Find by the way also

20
00:01:33,710 --> 00:01:39,290
returns a cursor, not a list of documents, that cursor is useful for manually going through the documents

21
00:01:39,470 --> 00:01:44,300
because otherwise all the documents which could be thousands or millions would have to be transferred

22
00:01:44,360 --> 00:01:50,130
over the wire in one go which would not be that great for your bandwidth and your connection.

23
00:01:50,690 --> 00:01:57,350
You can use filters on find and also on update and delete to narrow down which documents you want to

24
00:01:57,350 --> 00:01:57,830
find

25
00:01:57,860 --> 00:02:01,050
or you want to update or you want to delete.

26
00:02:01,090 --> 00:02:02,070
Last but not least,

27
00:02:02,200 --> 00:02:07,660
talking about retrieving data, you should be aware that you can use filters and operators, filters and

28
00:02:07,660 --> 00:02:13,430
operators basically allow you to narrow down the set of data you found like the greater than operator

29
00:02:13,570 --> 00:02:18,970
and you can identify all these special operators provided by mongodb by the fact that they start

30
00:02:18,970 --> 00:02:20,380
with a dollar sign

31
00:02:20,500 --> 00:02:26,200
and this allows you to simply limit the amount of data you are fetching. And you can use projection to

32
00:02:26,200 --> 00:02:32,650
then take the data you fetched and tell mongodb which fields you actually want to get and which you don't

33
00:02:32,650 --> 00:02:33,360
want to get,

34
00:02:33,400 --> 00:02:38,800
so filters allow you to restrict the amount of documents, projections then allow you to restrict the

35
00:02:38,800 --> 00:02:40,450
amount of fields per document

36
00:02:40,450 --> 00:02:43,470
so to say. These are the basics,

37
00:02:43,480 --> 00:02:44,560
let's now move on.