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You have completed Data Persistence with Room!
You have completed Data Persistence with Room!
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In this video we'll take a look at which queries we'll need to represent in our Data Access Objects!
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We've created all of our entities, which
represent the tables in our database.
0:00
Now it's time to create
the data access objects, or
0:05
DAOs, which represent the queries
we need for each of those tables.
0:08
But before we start creating anything,
let's talk about what queries we need, and
0:12
which table those queries belong to.
0:16
In main activity,
we display a list of all the pizzas.
0:20
To generate this list,
0:24
we'll need a query to select all
the pizzas from the pizza table.
0:25
Once we select a pizza,
we take that pizza's ID and
0:29
pass it into the creator activity.
0:32
Here, in order to display the pizza,
we'll need to retrieve its name,
0:35
as well as which toppings
are associated with that pizza.
0:38
To get the name, we'll use a query
to return a pizza by its id, and
0:42
then just access the name property.
0:46
But to get which toppings are on a pizza,
we'll actually need two queries.
0:49
[SOUND] One to get which topping
ids belong with our pizza id, and
0:53
then another to get which toppings
belong with those topping ids.
0:57
To populate the Recycler
view at the bottom,
1:01
we'll also need a query to
retrieve all the toppings.
1:03
Once a user has created their pizza,
they'll probably want to save it.
1:06
To handle saving a pizza,
we'll need two insert statements.
1:10
One for saving its data to
the pizza table, and one for
1:14
saving its toppings to
the pizza topping table.
1:16
Likewise, to let users delete a pizza,
we'll need queries to remove a pizza from
1:20
both the pizza table,
as well as the pizza topping table.
1:24
Last but not least,
to let us populate our topping table,
1:27
we'll need an insert statement.
1:31
It may seem like a lot of queries, but
1:33
broken out into which queries along with
which table, it's really not so bad.
1:35
Awesome, now that we know which
queries we need to create,
1:41
let's start creating
them in the next video.
1:44
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