Saving Data on Android

DELETE FROM
 query in 
your 
questions
 table. Since there is no 
WHERE
 clause, this will just delete all the 
records in your 
questions
 table, which is what you will need later.
Note
: Notice how, if you examine the query 
String
, there's some degree of 
autocomplete available. Room knows which entity definitions you've created 
and which fields exist within. You can use this to write queries, and to easily 
connect to those definitions, knowing that autocomplete is here to help you 
write them.
Room also offers the 
@Delete
 annotation to automatically create 
DELETE FROM
 
querys. A method annotated with 
@Delete
 will delete its parameter objects from the 
database. For example, if you wanted to delete a single question from your database, 
you could do something like this:
@Delete
 
fun
 
deleteQuestion
(question: Question)
Note
: If you want to learn more about 
@Delete
, you can check out the official 
documentation here: 
https://developer.android.com/reference/android/arch/
persistence/room/Delete.html
.
Finally, add the following methods:
@Query("SELECT * FROM questions ORDER BY question_id")
 
// 1
 
fun
 
getAllQuestions
()
: List 
 
@Transaction
 
// 2
 
@Query("SELECT * FROM questions")
 
// 3
 
fun
 
getQuestionAndAllAnswers
()
: List
Just like 
deleteQuestion()
, the above methods use 
@Query
 to create SQL 
statements. Taking each commented section in turn:
1. This statement is retrieving all the question records in your database and 
ordering
 them by 
question_id
. The response is returned as a 
List
 of 
Question
 
objects.
Saving Data on Android
Chapter 8: The DAO Pattern
raywenderlich.com
135

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2.
@Transaction
 tells Room that the following SQL statements should be executed 
in a