1. SQLite in Android
Landon Cox
March 2, 2017

2. What is storage?
Storage is persistent
Stored state retains its value across launches, reboots
Primary interface to storage: files
Files can be opened, read, written to, and closed
Databases are often implemented on top of files
Databases provide a higher-level storage interface (e.g., SQL)
Java provides a wealth of ways to interact with storage/files
Your code isn’t going to be very useful without storage

3. Launch Process killed Running Shut down onCreate() onStart()
onRestart()
onResume()
Process killed
Running
onPause()
onStop()
onDestroy()
Shut down

4. Saving quiz state Last time: we remembered which quiz we were taking
Apps will need to write to storage too
Users may expect to pick up where they left off if the app exits
What quiz state should you save in case the app exits?
Several ways to do this
SharedPreferences for simple key-value maps
SQLite for more complex kinds of state
SharedPreferences
Get a reference to SharedPreferences through Context
To write: edit, put*, commit
To read: get*
Last time: we remembered which quiz we were taking

5. Saving quiz state What else might we want to save?
Which quizzes we’ve taken
The user’s progress on each quiz
The user’s final score on completed quiz
How long the user took to complete the quiz
Using a key-value store for all of this will become unwieldy
Instead: use a relational database like SQLite!

6. Relational databases Data is organized into tables
Tables have named, typed columns
Data is stored as rows in a table
Can place constraints on columns (e.g., uniqueness)
Structure + constraints define the schema
Read/write the data base with SQL
Structured Query Language (SQL)
SQL is declarative
It describes what result you want, not how to compute it
Example databases: mysql, postgresql, sqlite

7. SQLite SQLite is the primary database for Android apps
Classes for managing your app’s SQLite database
Contract class w/ inner BaseColumns class
DbHelper class that extends SQLiteOpenHelper
Cursor for iterating through answers to queries

8. Define the contract/schema
Contract class
Place to put all constants related to your database
BaseColumns inner class
Table names
Column names
One BaseColumns class for each table in the db
_id
quiz_title
num_correct
num_wrong
last_question
finished_quiz
timestamp
Duke Basketball

9. Create the database SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);
$> ~/Library/Android/sdk/platform-tools/adb shell
$> su
$> sqlite3 /data/data/edu.duke.compsci290.quizmaster/databases/

10. Keywords: create, table
Create the database
SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Keywords: create, table
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

11. Table name: quizprogress
Create the database
SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Table name: quizprogress
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

12. Create the database SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Column name: _ID
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

13. Create the database SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Column type: INT
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

14. Unique to each row: PRIMARY KEY
Create the database
SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Unique to each row: PRIMARY KEY
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

15. Column name: quiz_title
Create the database
SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Column name: quiz_title
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

16. Create the database SQLiteOpenHelper class
Gives references to SQLiteDatabase instance
constructor: super call to create db
onCreate: create SQL command to create tables
Column type: TEXT
CREATE TABLE quizprogress (_ID INT PRIMARY KEY,
quiz_title TEXT,
num_correct INT,
num_wrong INT,
last_question INT,
finished_quiz INT,
timestamp INT);

17. Put information in the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can use insert method
INSERT INTO quizprogress (quiz_title,
num_correct,
num_wrong,
last_question,
finished_quiz,
timestamp)
VALUES (“Duke Basketball”, 0, 0, 0, 0, ) ;

18. Put information in the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can use insert method
Keywords: INSERT, INTO, VALUES
INSERT INTO quizprogress (quiz_title,
num_correct,
num_wrong,
last_question,
finished_quiz,
timestamp)
VALUES (“Duke Basketball”, 0, 0, 0, 0, ) ;

19. Put information in the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can use insert method
List of columns to update
INSERT INTO quizprogress (quiz_title,
num_correct,
num_wrong,
last_question,
finished_quiz,
timestamp)
VALUES (“Duke Basketball”, 0, 0, 0, 0, ) ;

20. Put information in the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can use insert method
INSERT INTO quizprogress (quiz_title,
num_correct,
num_wrong,
last_question,
finished_quiz,
timestamp)
VALUES (“Duke Basketball”, 0, 0, 0, 0, ) ;
Values for each column in new row

21. Read from the database SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use query method
SELECT _ID, timestamp
FROM quizprogress
WHERE quiz_title LIKE “Duke Basketball”
ORDER BY timestamp DESC;

22. Keywords: SELECT, FROM, WHERE, LIKE, ORDER BY, DESC
Read from the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use query method
SELECT _ID, timestamp
FROM quizprogress
WHERE quiz_title LIKE “Duke Basketball”
ORDER BY timestamp DESC;
Keywords: SELECT, FROM, WHERE, LIKE, ORDER BY, DESC

23. Columns in result: _ID, timestamp
Read from the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use query method
SELECT _ID, timestamp
FROM quizprogress
WHERE quiz_title LIKE “Duke Basketball”
ORDER BY timestamp DESC;
Columns in result: _ID, timestamp

24. Table to query: quizprogress
Read from the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use query method
SELECT _ID, timestamp
FROM quizprogress
WHERE quiz_title LIKE “Duke Basketball”
ORDER BY timestamp DESC;
Table to query: quizprogress

25. Filter rows using quiz_title
Read from the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use query method
SELECT _ID, timestamp
FROM quizprogress
WHERE quiz_title LIKE “Duke Basketball”
ORDER BY timestamp DESC;
Filter rows using quiz_title

26. Return results in descending order using timestamp
Read from the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use query method
SELECT _ID, timestamp
FROM quizprogress
WHERE quiz_title LIKE “Duke Basketball”
ORDER BY timestamp DESC;
Return results in descending order using timestamp

27. Update the database SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use update method
UPDATE quizprogress
SET timestamp =
WHERE quiz_title LIKE “Duke Basketball”;

28. Keywords: UPDATE, SET, WHERE, LIKE
Update the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use update method
UPDATE quizprogress
SET timestamp =
WHERE quiz_title LIKE “Duke Basketball”;
Keywords: UPDATE, SET, WHERE, LIKE

29. Table to use: quizprogress
Update the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use update method
Table to use: quizprogress
UPDATE quizprogress
SET timestamp =
WHERE quiz_title LIKE “Duke Basketball”;

30. New column value: timestamp
Update the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use update method
New column value: timestamp
UPDATE quizprogress
SET timestamp =
WHERE quiz_title LIKE “Duke Basketball”;

31. Specify which rows to update
Update the database
SQLiteDatabase
Can submit raw SQL queries w/ execSQL
Can also use update method
UPDATE quizprogress
SET timestamp =
WHERE quiz_title LIKE “Duke Basketball”;
Specify which rows to update