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Hello again.

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In this video, we will update entries and
delete entries in our tables to see

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how these actions may change
when working with relationships.

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If you closed your project, don't forget
to reactivate your virtual environment and

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then pop back into the Python shell.

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And go ahead and import models.

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Let's create some variables to
hold the entries we have so

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far to make things a bit easier.

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I'm gonna run a few queries that are also
in the teacher's notes to speed things up.

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So lion =, and

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I'm gonna copy-paste to make this
a little bit easier on myself as well.

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Models.session.query(models.Animal).filte-
r(models.Animal.name=="lion").

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And then you'll wanna put this dot first
in there, otherwise it's gonna give you

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a query object instead of the actual
thing you're looking for.

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So we hit that and we check lion.name,
just to make sure.

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Lion, perfect.

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Okay, I'm gonna go ahead and
copy-paste the rest of these.

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I'm pulling it straight from
the teacher's notes just like y'all,

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just to speed things up.

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So the other animal we had was wombat.

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wombat.name, just to check, perfect.

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I'm just gonna grab the first lion log, I
know that we put two in the database, but

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I'm just gonna grab the first one.

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.notes, great pouncer, perfect.

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And then the other log that we did for

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a different animal was where we did our
mistake one, which was first a seal.

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So we copy-paste that one,
seal_log.notes, likes to wave, perfect.

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Okay, we're all set up.

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Now that we've got our all of our
variables, let's try updating some values.

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Let's change the lion's habitat
from savannah to grasslands.

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I did want 100% google lion habitat to get
that answer, just being [LAUGH] honest.

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So lion.habitat = "grasslands", hit Enter.

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And if I do lion.habitat,
we get grasslands.

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And we can also check
models.session.dirty,

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which if you don't remember,
It's not callable, oops.

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It's just .dirty, there we go,
which holds our change.

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The session dirty is always what
holds any changes that you make until

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you commit them.

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So let's go ahead and
commit that to the database,

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models.session.commit, perfect.

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And then we can check
the lion_log.animal attribute,

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and it pulls up our changes as well.

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So they are reflected in the database.

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Pretty easy, right?

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It works pretty much the same
as it did with a single table.

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Let's try changing our wombat animal
into a seal so that our log and

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our animal actually make sense.

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So I'm gonna do seal, just so
that things are a little less confusing,

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I'm gonna do seal = wombat.

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And then we can do seal.name,
and you can see it says wombat,

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so we need to change that.

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seal.name = "seal",

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Ooh, not sale,
seal.name = "seal", there we go.

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And seal.habitat =, "ocean".

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And now let's do seal_log.animal,
and we get our changes.

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So if you see this zoo.db-journal,
don't worry about it,

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it just means that things
are moving with the database.

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So let's do our models.session.commit,
hit Enter.

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And you can see,
then it goes away, awesome.

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Lastly, let's see what happens if I
change seal_log.animal_id to number 1.

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If I then do you seal_log.animal,

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which is our relationship,
it's now pulling the lion.

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And if I do lion.logs,
I'm getting three logs now instead of two,

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great pouncer, really likes meat,
and likes to wave.

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So it's also important to know,
if you change what the foreign key is,

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it will attach itself
to a different entry.

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So something to keep in mind.

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I'm gonna go ahead and
reset that back to what it was,

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so seal_log.animal_id = 2.

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Let's do seal.logs, perfect.

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And just to make sure,
models.session.commit, Awesome.

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Now let's look at deleting some entries.

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Let's do models.session.delete(seal),

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so we're gonna delete an animal,
and models.session.commit.

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With that deleted, now let's see
what happens to the seal log.

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Let's do seal_log, I'm gonna print it.

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Okay, so you can see our Animal ID
is now None instead of 2.

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So if you delete the animal that relates
to your log, it's important to remember

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that that ID will then be switched
over to None instead of an integer.

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Let's try deleting lion log.

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models.session.delete(lion_log),

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models.session.commit.

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Okay, now we can look at the logs and
let's look, lion.logs.

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And we can see we only have one log now.

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The log is completely gone.

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So deleting entries will work the same
way, but will also affect relationships.

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But there's also something cool
that you can build into your model,

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it's called cascade.

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And we'll look into it
more in the next video.