7 hours 36 minutes
All right, Welcome back to model one course introduction. This is lesson to database engines and we're in the first and only sub lesson 2.2 database engine overview.
So what is a database while a database, if we look up the definition is a structure set of data held in a computer,
especially one that is accessible in various ways. Now that definition definition is very broad and would cover a lot of things. For example, you could put a bunch of data in excel and then call it a database. You could put a lot of data in a note pad and then call it a database
because essentially becoming just that a structured set of data held in the computer.
Now, what is a database engine? Well, a database engine. If we look up the definition of that, we get kind of a complicated definition.
So a database engine or storage engine is the underlying software component that a database management system D B. M s uses to create, read of dating, delete crowd
data from a database, so
toe put that much more simply.
Database engine is simply software that manages a database.
So there are a lot of those out there. There's my sequel, which we're going to be working with in this course. There's Microsoft sequel. There's the
There's the fire base that Google has. There are some other ones as well. So
which database should you learn or which database engines should you learn? Well,
we're actually kind of lucky that there are standards being pushed out with respect to what structured query language should support. And B,
what does that mean? That means that if you get really good at sequel in one database,
you'll be able to take a lot of what you know, into another database and acclamation to that database very quickly. Now, you might not get very specific questions correct right out the bit of the outer gate, because in one database you might have called a
a specific type of joint a Cartesian join, and then in another database that might have called it a cross joint. And if you've never thought of it as a cross joint, of course you're not aware of that. And so you see it and then you're like, OK, I know what that is. It's just that we call that something else over there.
So that means, is that we can learn and get really good at sequel in one engine and take a lot of what we've learned and apply in another engine pretty quickly. So just to give you an example,
let me pull up a query that we will use later on. In this course. This is a query written for my sequel
against the ACU Matic, a database they gets installed later as well,
so this will run in my sequel.
This is currently running against my sequel
Take This and I copy
and I go
into Microsoft sequel, which is now where we are right now, and I paste that Cleary.
I see a red squiggly line, but only one now. I just tried to run this query. I'll get there.
You don't say. The type sign is not defined system time,
which is the underlying word here. So signed is a type of energy or or number,
and Microsoft sequel doesn't call it that.
So to make this compatible with Microsoft's equal, we only need to change one thing. We need to change that sign to an imager
now, if we run it,
In fact, there's a way we could make this quarry working either database with no changes. We just give her the cast statement,
and this will still run.
Now we take it back into my sequel
and just paste it
in there as is.
It'll still run.
So both of these queries produce the same results and
send the data base engine the equivalent command, and we get the expected results, which are the same back shows how similar the sequel statements are between my sequel on Microsoft's equal and the same is true for Oracle and IBM. A lot of times you could potentially take the exact same query that you've written,
copy it and paste it into the other database. Another database will run just fine. Now there are other nuances, such as the cast statement as well as the limit one. For example,
if we, ah want to only get one record back,
we have to put limit one
my sequel and we get one record back. But if we wanted the same effects
and Microsoft sequel,
we select top one
and we get the same effect.
So there are little differences. Differences such as that, but the relationships stay the same. The 121212 many, many, many Cartesian products. They might give it a different name, like in one database. They might call it a cross joint,
but once you understand that, you'll recognize it is the same thing and adjust accordingly.
So that completes this lessons on database engines. We briefly describe what a database is. What a database engine is. Database is just a
basically a safe set of data, and it's very broad. Could include text documents, excel or databases them stata base engine data themselves. And then we discuss database Engine, which is software that specialized end out of a storage or crowd operations, which stands for create of date delete.
Basically putting that in the database.
The leading data, if necessary, and updating data
as well as retrieving it.
And we looked at how similar the sequel can be
can be between two different database engines
and why getting good at sequel in one database engine gives you a lot of ability and other database engines that follow the structure. Query language constructs is, well,
new ways that completes this lesson, and I hope to see you in the next thank you
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