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We're almost done creating our entities.

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All we've got left is one
combining pizzas with toppings.

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The first step to creating
an entity is to create a class.

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To get started, let's create a new pizza
topping class inside of our data package.

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And make sure to pick Class.

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Then, just like our other entities,
let's make this a data class.

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And declare our columns,
a parameters to the constructor.

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So instead of brackets,
we want parentheses.

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And inside the parentheses,
let's use a val to declare

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pizzaId as the first parameter,
and make it an Int.

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Then let's use another val,
to declare toppingId

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as the second parameter, and
let's make it an Int as well.

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Great, now let's add the @Entity
annotation above the class.

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And all that's left is to
declare the relationships.

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We'll need to specify the primary key,
as well as both foreign keys.

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Let's start with the primary key.

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In the previous video,

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we declared a primary key by
using the @primarykey annotation.

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However, this doesn't work if your
table has more than one column in its

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primary key.

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For situations like this
you have to declare

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the primary key up with the entity.

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Let's add parentheses
after the word entity, and

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let me just quickly hide the side pane.

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And then let's look at some of
the options we can declare.

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By default,

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each table in the database will be named
exactly like its corresponding entity.

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However, if you'd like the table
to have a different name,

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you can do that by specifying
the table name property.

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In addition to the table name, it looks
like there's also entries to let us

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specify multiple primaryKeys,
and multiple foreignKeys.

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Let's set up the primaryKeys by typing,

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primaryKeys = arrayOf.

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And inside the array, we just need
to add the names of the columns.

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PizzaId.

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And toppingId.

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Also inside annotations, and
only inside of annotations,

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we're allowed to declare
a raise using brackets.

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Let's use alt+enter on
arrayOf to replace this call

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with an array literal,
which are the brackets, awesome.

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Now, to add a comma at
the end of our array.

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And then add a new line for
setting up our foreign keys.

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Let's type foreignKeys=, and remember it
needs an array of foreign key objects.

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Let's add the brackets for the array, and
then create a new foreign key by typing,

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[(ForeignKey)], and
hitting enter to accept auto complete.

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Which for some reason,
gives us an extra couple of parentheses.

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Let's get rid of those.

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And then look at which
parameters we need to provide.

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We’ll need to specify the first three.

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The entity the foreign key represents,
the name of the column and

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the parent table, and
the name of the column and this table.

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Referred to as the child columns.

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Also, even though in this case we're only
matching one column with one other column,

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it's possible to have a foreign
key involving multiple columns.

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So instead of just using a string,

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we'll need to specify each of these
columns as an array containing a string.

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Okay, let's start with
the pizza foreignKey.

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Its entity is the pizza class.

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So, let's set entity = pizza:: class,

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parentColumns = to an empty array.

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The parent column is just
the name of the column that

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the foreign key is referencing.

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Since the pizzaId column corresponds
to the id column in the Pizza table,

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that's the one we're looking for.

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Let's add id to our parentColumns array,
and then move on to child columns.

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Which is just our pizzaId column.

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So let's add a comma, and
then set child columns

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equal to an array containing
pizzaId as a string.

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All right, all we've got left
is to specify our foreignKey

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to the topping table.

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I'm gonna add a bit of spacing to
make it easier to see everything.

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Then let's copy our pizza foreignKey,

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add a comma to the end of the line,
and then paste it on the next line.

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Now we've just gotta
change pizza to topping,

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and a pizzaId, to toppingId,
and there we go.

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The pizza topping table is finished.

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Pretty cool, right?

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We've created a bunch of tables, but
we haven't had to right any SQL.

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Thinking back to the last video,
once we've created the end of these,

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it's time to create the dows.

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Coming up, we'll take a look
at how to query our tables

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by using data access objects.