SQLite

SQLite is a lightweight, embedded, SQL database engine that comes pre-installed on Android devices. It's a popular choice for storing structured data locally within your Android apps.

Key Concepts:

1. SQLiteOpenHelper:
   
   

   • A helper class that manages the creation and upgrade of the database.

   • It provides methods to:

     • Create the database

     • Upgrade the database schema

     • Get a readable or writable database instance

2. SQLiteDatabase:
   
   

   • Represents an open database.

   • Provides methods for:

     • Executing SQL queries

     • Inserting, updating, and deleting data

     • Querying data

3. ContentValues:
   
   

   • A class for holding key-value pairs of data to be inserted or updated in the database.

Steps to Use SQLite in Android Studio:

1. Create a SQLiteOpenHelper Class: 

Java

public class MyDatabaseHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "mydatabase.db";

    public static final int DATABASE_VERSION = 1;

    public MyDatabaseHelper(Context context) {

        super(context, DATABASE_NAME, null, DATABASE_VERSION);

    }

    @Override

    public void onCreate(SQLiteDatabase db) {

        String CREATE_TABLE_QUERY = "CREATE TABLE mytable (" +

                "id INTEGER PRIMARY KEY AUTOINCREMENT," +

                "name TEXT," +

                "age INTEGER)";

        db.execSQL(CREATE_TABLE_QUERY);

    }

    @Override

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)  

{

        // Handle database upgrades  

here

    }

}

2. Get a Database Instance: 

Java

MyDatabaseHelper dbHelper = new MyDatabaseHelper(context);

SQLiteDatabase db = dbHelper.getWritableDatabase();

3.Perform CRUD Operations:

• Insert Data:

Java

ContentValues values = new ContentValues();

values.put("name", "Alice");

values.put("age", 30);

long newRowId = db.insert("mytable", null, values);

Query Data: 

Java

Cursor cursor = db.query("mytable", null, null, null, null, null, null);

while (cursor.moveToNext()) {

    String name = cursor.getString(cursor.getColumnIndexOrThrow("name"));  

    int age = cursor.getInt(cursor.getColumnIndexOrThrow("age"));

    // Do something with the retrieved data

}

cursor.close();  

Update Data: 

Java

ContentValues values = new ContentValues();

values.put("age", 35);

String selection = "name = ?";

String[] selectionArgs = {"Alice"};

int count = db.update("mytable", values, selection, selectionArgs);

Delete Data: 

Java

String selection = "id = ?";

String[] selectionArgs = {"1"};

int count = db.delete("mytable", selection, selectionArgs);