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To start writing queries, we first need
to create the data access objects.

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Let's start with creating the Dao for
our topping table.

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In Android, we create a data
access object as an interface, so

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inside our data package.

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Let's create a new interface
called ToppingDao.

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Make sure to pick Interface.

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Then to designate it as
a data access object,

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we just need to add the @Dao annotation.

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And hit Enter to import it.

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Inside the interface, we'll declare
each of our queries as a function

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with an annotation to tell
room how to handle the query.

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Let's see how it works by creating
a query to select all the toppings.

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Let's add a function called getAll,
fun getAll and

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let's make it return a list of toppings.

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Remember since this is an interface,
we don't need to add a function body.

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Then to tell room how
to get the results for

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this function,
let's add a line above this one.

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And add the @Query annotation and
some parentheses.

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And inside the parentheses, we just
need to declare our query as a string.

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So let's type select * from topping.

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And there we go.

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We've got a function that will return all
of the toppings and the topping table.

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Also notice that we have syntax
highlighting in our SQL.

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Thanks to room,

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Android now has a few checks to make sure
queries are correct before we run the app.

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It even knows what tables we have.

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So if I accidentally change this toppin,
we'll get an error.

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All right, let's move on to selecting
a specific topping by its ID.

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Let's add a couple of lines
below our getAll function and

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then create a new function
called getTopping, By Id,

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then let's add an ID parameter as in Int,
and make sure it returns a topping.

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Moving on to the query,
let's add the annotation.

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And then add the query itself.

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Let's go with select * from topping,
where id equals, and

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this is where we need to
use our id parameter.

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To reference a parameter in a query,
you just prefix it with a colon.

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So let's add colon id.

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And now we can get a specific
topping just from its id.

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To finish up our ToppingDao,
all we need is an insert statement.

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Represented as a function, it would
take in a topping and return nothing.

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Let's add a couple lines at the bottom and

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then declare a new insert function
to do just that, fun_insert.

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And it will take in a topping.

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And return nothing.

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Then to tell room how
to handle the insert,

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there's actually a special
@Insert annotation.

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So all we need to do is add @Insert,
and we're done.

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Great work finishing your
first data access object.

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I know it might feel like a lot, but

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one way to make sure you really understand
something is to get some practice.

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Why don't you try to create
the other two dials on your own?

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You can find the required queries below,
in the teacher's notes.

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I'll show you how I do
it in the next video.