Django Tutorial for Beginners - 8 - Activating Models Video Lecture | Django: The Ultimate Beginners Guide - Back-End Programming

wait a minute I remember from the last
tutorial Bucky you said that whenever we
make AB right after we make the template
for it we need to go and websites and
settings right here and then we need to
go ahead and put it in installed apps so
that way whenever we boot up our server
it's going to go and say okay let me go
ahead and check out your installed apps
and make sure they're all working with
the database correctly so what you do
here is you just write the package name
or the app name which is music and then
check the cells so it's music apps music
config so that's where that
configuration file comes in apps music
config so again this just refers to this
app basically all right now
don't forget your comma right there and
you may be thinking right now all right
everything looks good I mean we have our
template right there and we make sure to
do this so let's just go ahead and boot
this server up but you remember in the
last tutorial whenever we did that it
said give us a little issue because it
said all right these migrations are not
applied or it said something like that
well that's what's going to happen if we
just boot it up right now because what
happens whenever you start your server
is it goes in it looks right here and
for each app that's installed it's going
to go look at those models and check to
see that these models match the database
and right now they don't because even
though we defined our template or
blueprint right here we didn't reflect
that in our database structure so that
is kind of the last piece of the puzzle
that's where those migrations or changes
come in so how do we do that is the
easiest thing ever just type Python
manage py and type make migrations music
so what we're doing in this command is
we're just telling django hey we made
some changes to the music model in this
case what we did is we just added two
classes and if we go ahead and hit enter
then what's going to happen is this it
says ok I made these migrations in other
words I made these changes right here
and if you guys don't know what a
migration is then you guys don't have to
type this if you don't want but I'm
going to show you and this probably is
going to make everything click for you
so if I go manage Beppe UI SQL migrate
music 0 0 0 1 because that's what this
ID number is right here look at what it
is so all the migration is basically
taking whatever changes you have and it
converts them to a SQL file so you see
what it's doing in this case is creating
a table for albums creating a table for
songs and it's creating a bunch of
columns so again a migration is just a
change to your dad base that's it
that's all we're doing whenever we're
talking about migrations make these
migrations whatever so now we have this
SQL file or change file created now all
we have to do is actually just run it
like you're running a SQL file so this
is what we did in the last tutorial
Python managed py migrate so again the
first command makes the change file in
this command right here actually runs it
so it says apply all migrations running
the migrations basically now our
database is synced with this code so now
check out what happens whenever we run
our server we run and we do not have any
issues so again one last time what
happens is whenever your website first
starts up whenever your server first
gets booted up what's going to happen is
it's going to go and it's going to look
at a website
settings so it's going to scroll down
here and look at all of your installed
apps now for each installed app it's
going to go and it's going to look at
that model so it's going to review it
and it's going to make sure that this
structure right here the structure of
whatever data you're working with in
your code reflects whatever data you can
save in your database if it doesn't sync
up then that's when it gives you that
error if it does then everything runs
fine
so again if you ever see that error then
what you need to do is you just need to
make your migration file and then just
run it and if all that sounds confusing
all you have to remember is three steps
whenever you need to make a change to
your database structure just go ahead
and make the change in code right there
and then you write two lines the first
one is make migrations where are yet
make migrations and then migrate that's
it so again any time you want to make a
change this make the changes in the
models that py file make migrations in
my grade so just let django know that
you made some changes and apply them to
the database boom roasted you will be
good to go working with databases is a
piece of cake trust me i'll see you guys
in next video