00:01 Let's begin our exploration of MongoDB at a high level
00:04 with the why and history of NoSQL in general.
00:08 So if you look around the software development landscape
00:11 you'll see that people when they talk about
00:13 how are we going to design our application frequently say
00:15 well let's assume that we have a relational database,
00:18 now we can discuss what type of ORM should we use,
00:22 or should we use an ORM at all,
00:24 or should we use micro services or things like this.
00:26 Basically, the fact that we're starting from a relational database
00:29 is considered to be an axiom of software development,
00:33 we have data, it goes into relational database
00:35 now let's talk about the architecture, now let's talk about scaling,
00:38 let's talk about performance and so on.
00:40 And just to drive home how strong of a statement that is,
00:42 an axiom, recall the exact definition—
00:45 a statement or proposition that is regarded as being self evidently true,
00:49 it's just clear that you start from a relational database.
00:52 So what are the things I hope you take away from this course is
00:55 that the database style, the database engine is a choice,
01:00 it's a really important choice that has actually super important
01:04 and far reaching implication for your application.
01:06 So I want to sort of break this mold
01:09 that starting from a relational database is an axiom.
01:12 Sometimes it makes sense, sometimes it's perfect,
01:15 but a lot of times as you'll see throughout this course
01:17 starting with a document database is actually a better choice.
01:20 Now, what is NoSQL? Ask five people what NoSQL is,
01:24 you'll probably get five different answers back.
01:26 Some people will say, well the 'no' stands for 'not only'
01:31 so NoSQL is 'not only SQL',
01:34 well that's a great open minded view of the world,
01:37 but I'm sorry to say that's not what NoSQL is.
01:40 Maybe it means it doesn't have SQL,
01:44 maybe it means the system operates without the SQL language, right,
01:47 without select * from this etc, without that language.
01:51 If we look at the history, I think you'll see that this is also not the case.
01:55 Here's a toaster, this toaster operates without SQL,
01:58 is it a NoSQL toaster— I don't think so!
02:01 And of course not, it's not a NoSQL toaster, it's just a toaster.
02:05 NoSQL doesn't mean it operates without the SQL query language
02:08 in fact, I believe that document DB, Microsoft's document database
02:13 that runs in Azure, actually more or less uses
02:16 a flavor of the SQL query language to query it.
02:19 So no, it's not about excluding this SQL query language,
02:22 it's something entirely different, so let's next look at the history,
02:26 and I think you'll have a really good idea of what NoSQL is
02:29 and maybe it will come to a little bit closer agreement on the definition of NoSQL.