SQLite Database Tutorial
Introduction to SQLite
SQLite is a C-language library that implements a small, fast, self-contained, high-reliability, full-featured, SQL database engine. It is the most used database engine in the world. SQLite is built into all mobile phones and most computers and comes bundled inside countless other applications that people use every day.
Setting Up SQLite in Android
In Android, SQLite is a native database used to persist data. It is available by default on all Android devices. To create a database, you will use the SQLiteOpenHelper class.
Example
Below is a basic example of how to set up an SQLite database in an Android application.
public class MyDatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "example.db";
private static final int DATABASE_VERSION = 1;
public MyDatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS users");
onCreate(db);
}
}
Creating and Managing Database
To manage your database, you will use the SQLiteDatabase class. This class provides methods to perform CRUD (Create, Read, Update, Delete) operations.
Example
Below is an example of how to insert data into the database.
SQLiteDatabase db = myDatabaseHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", "John Doe");
values.put("age", 30);
long newRowId = db.insert("users", null, values);
Reading Data from the Database
To read data from an SQLite database, you use the query() method or the rawQuery() method.
Example
Below is an example of how to read data from the database.
SQLiteDatabase db = myDatabaseHelper.getReadableDatabase();
String[] projection = {"id", "name", "age"};
Cursor cursor = db.query("users", projection, null, null, null, null, null);
while (cursor.moveToNext()) {
long itemId = cursor.getLong(cursor.getColumnIndexOrThrow("id"));
String itemName = cursor.getString(cursor.getColumnIndexOrThrow("name"));
int itemAge = cursor.getInt(cursor.getColumnIndexOrThrow("age"));
// Use the data
}
cursor.close();
Updating Data in the Database
To update data in an SQLite database, you use the update() method.
Example
Below is an example of how to update data in the database.
SQLiteDatabase db = myDatabaseHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", "Jane Doe");
String selection = "id = ?";
String[] selectionArgs = { "1" };
int count = db.update("users", values, selection, selectionArgs);
Deleting Data from the Database
To delete data from an SQLite database, you use the delete() method.
Example
Below is an example of how to delete data from the database.
SQLiteDatabase db = myDatabaseHelper.getWritableDatabase();
String selection = "id = ?";
String[] selectionArgs = { "1" };
int deletedRows = db.delete("users", selection, selectionArgs);
Closing the Database
Once you are done with your database operations, it is a good practice to close the database using the close() method.
Example
Below is an example of how to close the database.
myDatabaseHelper.close();
Conclusion
In this tutorial, we covered the basics of setting up and using an SQLite database in an Android application. We learned how to create, read, update, and delete data from the database. By following these steps, you can effectively manage data persistence in your Android applications.