Now that's it for this course section.
In this course section,
you got a thorough introduction into SQL
and the kind of databases that use that language.
Most importantly, MySQL,
which we installed and started working with.
Though, I want to mention again,
that what you learned about the SQL Syntax in this
section here, will apply to all the SQL databases
you might be using.
It's a very popular and common database system,
and therefore definitely a system or a language,
you have to know when being a Web Developer.
You'll learn that when you work with a relational database
management system, as we did it here in this course section,
that it's all about working with different tables.
Storing your data in a normalized form,
which means in a simplified form, where you have no complex
data in a single table across multiple tables,
linked together through IDs or other unique identifiers,
as we did it in this course section.
And you then learn how you can run commands to create
tables, to insert data into tables,
to update or delete data, and of course, to query data.
To query data just like that,
or with constraints or counting the data that's
in a database table.
And then since we do work with multiple tables, of course,
you also learned about the very important
inner join statement, which allows you to
merge data together in your result sets
with which you then might be working in your applications.
So that you can answer questions like,
what's the name of the restaurant that has a rating of five?
For example.
Now coming back to these relationships.
In this core section,
we saw the one to many relationship and action,
which means that one record in table A can be related to
multiple records in table B.
For example,
that a single restaurant can have multiple reviews,
but every review belongs to only one restaurant.
There also are other kinds of relationships.
For example, one-to-one relationships.
There, you would have one record
in table A that's related to
exactly one other record in table B,
and not more than one record.
An example could be a team that has one team leader,
and that team leader leads exactly one team and team leaders
and team data is stored in different tables.
And last but not least,
you could also have many to many relationships,
which is a bit more advanced and therefore was not
covered here, but which you will always encounter,
if you dive deeper into web development and take dedicated
sequel courses or deep dive courses in general.
The idea behind many to many relationships is that a record
in table A can be related to multiple records in table B
and vice versa.
To handle this with a SQL database,
you would have an intermediate table
that stores the connections.
And an example would be,
a restaurant that has many customers
and every customer might visit many restaurants.
This is just a side note here.
It's not too important.
And we will come back to these relationships later
in the course, once we do dive in deeper.
And once we do build our online shop, for example.
I just wanted to mention them here already,
because of course a main feature off SQL databases of
relational database management systems,
as the name already implies, I guess,
is that you do work with relationships and that you do
relate data from different tables.
And therefore now, with that in the next chord section,
we're going to see how we can now actually use what we
learned in this section,
inside of a real application, inside of node JS code.
So that we don't have to write all the queries here in the,
MySQL workbench, which is nice for playing around,
but which isn't a real application and that we instead see
how we can actually do work with the database from inside
our node JS code.